Tuesday

March 31, 2015

March 31, 2015

Total # Posts: 11,123

**Maths**

Put x=5-7y Substitute in the circle (5-7y)²+y²=15 Solve for the two values of y. Find corresponding values of x to give two ordered pairs which are solutions to (a) for P and Q. For (b), use the mid-point formula M=((x1+x2)/2, (y1+y2)/2) If you need further help, ...
*March 2, 2015*

**Calculus 2**

First step: decompose into partial fractions (probably the hardest part of the problem) Factorize the denominator (if possible) x^3+x^2+x+1=x^2(x+1)+1(x+1)=(x^2+1)(x+1) so we can decompose the given fraction into: 1/(x^3+x^2+x+1) =1/2(x+1) + (1-x)/2(x^2+1) which can be ...
*March 2, 2015*

**matLab**

If you know the syntax for plotting in Matlab, then it would be similar to your previous problem in the name of Jasmine.
*March 2, 2015*

**MatLab**

* n=11, or Sum(11)
*March 2, 2015*

**MatLab**

Do you mean y=Σ 2^n/n for n=1,3,...11 ? If you are already familiar with the syntax of Matlab, you can use the following pseudocode: function [S] = Sum(n) sum=0; for i=1:n:2 sum=sum+2^i/i; end S=sum; end The calling program has to supply i=11 to evaluate the required ...
*March 2, 2015*

**Math**

I interpret "adding the square root of 16 and -8" as "adding the square root of 16 and the square root of -8" which gives sqrt(16)+sqrt(-8) = 4+2√2 i which is a complex irrational number. If I interpret "adding the square root of 16 and -8" ...
*March 1, 2015*

**math**

Use the mortgage payment formula: and assume 2% is per annum and compounded monthly, A=PR^n(R-1)/(R^n-1) where A=monthly payment ($850) n=number of months (=30) P=principal (amount borrowed) R=monthly interest rate + 1 =(0.02/12+1) Solve for P P=A(R^n-1)/(R^n(R-1)) It should ...
*March 1, 2015*

**Math**

All correct, to the nearest tenth of a degree.
*February 26, 2015*

**Calculus II**

The hydrostatic pressure at a distance of x, measured along the plate from the top of the plate is P(x)=ρg(6m + x sin(30°)) For a horizontal strip of width dx, and length w (=3 m), the force is dF=pressure × area =P(x)*w*dx =P(x)*w*dx Total force = ∫dF =∫...
*February 26, 2015*

**Please help and explain engineering science n3**

Component of force acting down the incline F1 = mg sin(θ) Normal component of weight (affects friction) N = mg cos(θ) Frictional force Fr = μkN Force exerted by engine to overcome gravity and friction F= Fr + F1
*February 26, 2015*

**Math**

Sine rule states that: sin(A)/a = sin(B)/b = sin(C)/c Here you are given both a and A, so knowledge of c will let you solve for sin(C). Sin(C)=c*(sin(A)/a)=0.96225 and sin-10.96225=74.207° or 105.793° since sin(x) is symmetrical about 90°. If the sum of the larger ...
*February 24, 2015*

**physics**

If you used 47kg and 37 degrees, you need to redo your calculations. Check your calculator for the trig functions to see if it is set in degree mode. In degree mode: cos(60)=0.50000000 In radian mode: cos(60)=-0.95241298...
*February 22, 2015*

**physics**

(45.0)*(9.80)*(sin35 degrees)= a number 45kg or 47kg?
*February 22, 2015*

**Pre-Calculus (Trigonometry)**

You're welcome! :)
*February 22, 2015*

**Pre-Calculus (Trigonometry)**

The sine curve is symmetrical about 90 degrees. So sin(x) has the same value as sin(180-x). Review of the unit circle will certainly help as well.
*February 22, 2015*

**Algebra 2**

See other post please.
*February 22, 2015*

**No alias please**

Nancy, Ann, Brooke, etc. We prefer you to use a single name at this site for continuity. Thank you for your cooperation.
*February 22, 2015*

**Algebra 2**

Use the rules of logarithm (any base): log(a)-log(b)= log(a/b) and the definition of log to the base a log_a(b)=x means a^x=b where a>0. So log_2(x^2-20)-log_2(x)=3 means log_2((x^2-20)/x)=3 now you can apply the definition of logarithm to solve for x.
*February 22, 2015*

**Trigonometry (Logarithmic Function)**

Rules of logarithm if log(a)=x, then log(a^2)=2x, ... log(a^n)=n×log(a) Similarly, if log(a)=x, then log(√a)=(1/2)x...
*February 22, 2015*

**math**

Correct! Well done.
*February 22, 2015*

**Math**

We have a problem with an integer solution. Use proportion/ratios, 2 boys to 3 girls means 2 boys to 5 total number of members. 2:5 = 4:10 = 6:15 .... try until the total number of members x is 20<x<30.
*February 22, 2015*

**Algebra 2**

Your steps are correct if the equation was: 8^(2x-1) = 16^(x+1) and assuming this is the case. Since 8=2^3, and 16=2^4, you can simplify further using the same rule of logarithms: log(a^b)=b×log(a)
*February 22, 2015*

**Algebra 2**

Grouping has to be done in such a way as to have a common factor. With cubics, the usual strategy is to find an obvious factor, then reduce the cubic to a quadratic by synthetic (or long) division. The first factor is to check for (x-1). If all the coefficients add to zero, ...
*February 22, 2015*

**Algebra 2**

I notice that the sum of all the coefficients is zero. Do you know how that would help?
*February 22, 2015*

**Algebra 2**

Have you done factoring of polynomials?
*February 22, 2015*

**Algebra 2**

x^2 - 3x^2-22x+24=0 is a quadratic with two like terms. Would you like to double check for typos?
*February 22, 2015*

**math**

Now you can take the time to reread and understand the question. What is the length if the width is x? Take the sentence "length is five less than two times the width" and replace the word "width" by x (that we defined above), and translate it to mathematics.
*February 22, 2015*

**math**

Put x = width of the garden then what would be the length in terms of x?
*February 22, 2015*

**Math**

It doe not look too clear what P and Q are, I am assuming the following. P=(4,3,0) Q=(0,6,6) PQ = Q-P = <4,-3,-6> by subtraction = 4i-3j-6k in unit vectors. Length of vector <x,y,z> = sqrt(x^2+y^2+z^2)
*February 22, 2015*

**statistics**

Let event A=pump A is working B=pump B is working Assume pumps A and B are independent. then A'=pump A is not working B'=pump B is not working, hence P(A')=0.1 (probability that pump A fails) P(A)=1-0.1=0.9 (probaility that pump A works) P(B')=0.2 P(B)=1-0.2=0....
*February 22, 2015*

**Maths**

Hmm, let me see. f(-2)=0, check f(1)=0, check f(2)=0, check when expanded, the leading coefficient is 2 (polynomial=2x³-2x²-8x+8) This checks too. Yes, your answer is correct.
*February 18, 2015*

**Math**

Hint: The factors of a number, say 12, are 1,2,3,4,6,12, or rearranged differently, 1,12, 2,6, 3,4 for a total of 6 (even). The factors of a prime number, say, 23, are 1,23 for a total of 2 (even). The factors of another composite, say, 36, are 1,2,3,4,6,9,12,18,36, or ...
*February 18, 2015*

**physics**

When the ball reaches the highest point, it means that its vertical velocty v1 is zero. With an initial velocity of v0 (upwards), and an acceleration due to gravity of -g (downwards), we use the relation v1=v0+at substituting v1=0, v0=16.5 and g=-9.81, you would be able to ...
*February 18, 2015*

**Math**

Please see you later post.
*February 18, 2015*

**Math Help Please**

"solve" involves at least one equation and one unknown. I think you mean "simplify the expression". Also, according to PEMDAS, you need parentheses when dividing a polynomial by a binomial, and the division is written on a single line (as you do when you ...
*February 18, 2015*

**Math**

This is also the handshake problem. Use the logic of the answer to the previous post.
*January 19, 2015*

**Math**

This is the same as the hand-shake problem. N people talked to N-1 people. But each call involves two people, so the number of calls is N(N-1)/2.
*January 19, 2015*

**physics**

g is not required if the bike is on a horizontal road. velocity = 1.3*10^3 m / (14 min * 60 s/min) = (65/42) m/s Kinetic energy = (1/2)mv^2 = (1/2)(57.1)(65/42)^2 J
*January 19, 2015*

**Algebra 2**

f(x)=5x+3 g(x)=6x-2 fxg(x)= (5x+3)(6x-2) Expand and simplify. The domain of a polynomial is (-∞,∞)
*January 14, 2015*

**Algebra 2**

f(x)+g(x)=-5x-4 + 6x+7 You can simplify and make your answer choice from the list.
*January 14, 2015*

**ALGEBRA**

Please write in upper/lower case. It's easier to read. Here's an example to help you solve the given problems. Factorize (x+2)^2-5(x+2)-14. Keep the (x+2) as a single entity, say y=(x+2), then (x+2)^2-4(x+2)-12 =y^2-4y-12 =(y-6)(y+2) Now substitute y=x+2 =(x+2-6)(x+2+2...
*January 14, 2015*

**Algebra**

You can solve it like almost any equation, but replacing the equality sign with \≠. For example, solve for q in (4a+3)/5≠3 so we can continue 4a+3≠5*3 4a≠15-3 4a≠12 a≠3 is the answer. In set notation, a ∈ R\3, or a ∈ (-∞,3)∪(3,∞) (...
*January 14, 2015*

**chemistry**

The solubility of gases in water depend on the atmospheric pressure and the ambient temperature. Here's a link to the solubility of various gases (in g/1000g water). http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html
*January 2, 2015*

**maths**

Before 10:15, only car is on the road, by which time it has travelled 80*(15/60)=20 km towards B. So remaining distance as of 10:15 is 150-20=130 km. When lorry starts, they approach each other at a total speed of (80+40)=120 km/h. Elapsed time (since 10:15) when they meet is ...
*December 31, 2014*

**java programming**

Which sorting algorithm do you plan to use? For small number of items (less than 200), bubble sort is easy to understand and code using for-loops. For large number of random items, quick sort could be used, but requires the understanding of recursivity.
*December 30, 2014*

**Medical billing/coding**

Try http://www.findacode.com/ to help you look up the codes if you don't have access to any. Do remember that if you are coding for medical billing, you need the codes for acts performed, not the diagnoses.
*December 30, 2014*

**Math/ Statistics**

The null hypothesis is generally an equality, which makes it: H0: The average attendance at home games equals 3000. However, when the alternative hypothesis is one sided, which in this case is: H1: The average attendance at home games is less than 3000. It will be understood ...
*December 30, 2014*

**math**

Please check if what is needed is P(x1/x2<0.5) or is it P(xi/xj<0.5) because otherwise x3 is not playing any role.
*December 28, 2014*

**math**

It looks to me this is an incompatible mixture of the two previous problems. f(x)≠(x+1)/2 if X~N(6,4). Please explain or elaborate if I am mistaken.
*December 28, 2014*

**math**

See response to previous post: http://www.jiskha.com/display.cgi?id=1419789148
*December 28, 2014*

**math**

Look up normal probability table for X~N(6,4) for P(X<8)=0.69 (approx.), so P(X>8)=0.31. Since we have random samples which we assume to be independent, we can use binomial probability distribution to calculate P(max{x1,x2,x3}>8). Alternatively, we can calculate P(all...
*December 28, 2014*

**math**

Given f(x)=(x+1)/2, -1<x<1 and zero elsewhere. So for each individual sample, P(X>0)=∫f(x)dx from 0 to 1 =∫(1/2)(x+1)dx =(1/2)[x²/2+x] 0 to 1 =3/4 = p Assume x1...x5 are independent and random samples, binomial theorem is appropriate: P(four of 5 X >0...
*December 28, 2014*

**programming**

Programming is a subject learned by intuition (for geniuses) or by practice (most of us). If your teacher did not cover programming, then it must have been required as a prerequisite. The problem given is not even for a first course in c-programming, so you will have a lot of ...
*December 26, 2014*

**programming**

What course are you taking, and which topics have been covered? It looks like this is an assignment to help you understand and apply what you have learned. I believe you should be able to show us some code or at least some pseudocode and start getting help with difficulties ...
*December 26, 2014*

**probability**

Let's simplify the problem to having 7 red balls, 5 green balls, and 4 blue balls (for a total of 16). Find the probability of drawing 2 red balls, 2R 2 green balls, 2G 2 blue balls, 2B (total of 6 balls), then Below we will use the notation of (n,r)=combination (n,r) =n...
*December 26, 2014*

**algebra**

Here we have two samples from two populations and would like to determine if the means are the same, namely to accept or reject: H0: μ1-μ2=0 The sample size n=14 is not sufficient to justify normality using the central limit theorem. Either an assumption of normality has...
*December 25, 2014*

**computers**

One possible cause is that the remote server administration tools are not installed on Windows 8 or 8.1. By default, they are not. If that's the case, the Active directory utilities, users etc will not be available. The fact that it pings the file server means that it is ...
*December 23, 2014*

**math**

Correction to missing parentheses for above expression for Z Z=[(X̄1-X̄2)-(μ1-μ2)] / sqrt(σ1²/n1 + σ2²/n2)
*December 19, 2014*

**math**

We have two samples, n1=n2=25 both are normally distributed, and are independent. Under these given conditions, E(X̄1-X̄2)=E(X̄1)-E(X̄2)=μ1-μ2 VAR(X̄1-X̄2)=V(X̄1)+V(X̄2)=σ1²/n1 + σ2²/n2 Z=(X̄1-X...
*December 19, 2014*

**Probability**

the equation you need is P(X=r)=C(n,r)*p^r*(1-p)^(n-r) C(n,r)=n!/((n-r)!r!) and n!=n(n-1)(n-2)....(2)1=factorial n You have everything you need to calculate the required probability. It turns out that C(n,0)=1 for any positive value of n. The answer is less than 5%. You can ...
*December 17, 2014*

**Math**

The rule of 72 says that the time in years it takes to double your money is 72 divided by the interest rate in percent. However, it applies to compound interest, but it still gives an approximate number of 100=72/x or x=0.72%. To calculate accurately, we use Future amount =Pe...
*December 17, 2014*

**Algebra**

add: ...and the remaining 24 variables equal to zero.
*December 13, 2014*

**Algebra**

Because it is circularly symmetrical, all 26 variables cannot have the same value (otherwise the sum would be zero). To maximize the value of |a-n|, we need |a-n|=10 which in the integer domain gives ±(0,-10),±(1,-9),±(2,-8),...±(5,-5),
*December 13, 2014*

**geometry**

A hexagon consists of 6 equilateral triangles. Therefore the side of each triangle is 24/6=4 units which also equals the radius of the circumscribed circle.
*December 13, 2014*

**geometry**

AU+UQ=5*AU UQ=26 so 26+AU=5*AU solve for AU.
*December 13, 2014*

**Statistics**

Baye's theorem P(P|Q)=P(P∩Q)/P(Q)=P(Q∩P)/P(Q) =P(Q∩P)/P(P)*(P(P)/P(Q)) =P(Q|P)*(P(P)/P(Q)) or simply P(P|Q)=P(Q|P)*(P(P)/P(Q)) Here P=stereo came from company A Q=stereo is defective So P(P|Q) probability that the stereo came from company A given that it is ...
*December 12, 2014*

**Physics**

Connected in series means the resistances could be added. Equivalent resistor = 4+10=14Ω Voltage = 12 V Assuming battery has zero internal resistance, V=IR, or I=V/R = 12/14 A = 6/7 A.
*December 11, 2014*

**Physics**

Length L = 6m Angle with horiontal, θ = 50° Friction with wall = 0 Coefficient between ladder and floor, μ = 0.5 Mass of ladder = M Mass of man, m = 11M Let the man climbs up X m. from the bottom, Vertical reaction of floor, R = M+11M=12M (because wall is smooth) ...
*December 11, 2014*

**Lat math question for some days. Can y'all help?**

No problem!
*December 9, 2014*

**Lat math question for some days. Can y'all help?**

Didn't you get an answer last time: http://www.jiskha.com/display.cgi?id=1416267535
*December 9, 2014*

**French**

Sorry, the codes didn't show, hope it is better this time: Some hints: (skip the blank spaces after & and before ;) à write & agrave ; è write & egrave ; é write & eacute ; ô write & ocirc ;
*December 9, 2014*

**French**

Some hints: (skip the blank space before ;) à write à ; è write è ; é write é ; ô write ô ; etc. Most of the verbs used are conjugated with the verb être, which means that you need to match the form of the verb with the ...
*December 9, 2014*

**French**

Please post your work so we can give you help instead of doing it for you. If you have difficulty with a certain aspect, please explain.
*December 9, 2014*

**Algebra please?**

How do you propose to do it, using a calculator, or by hand (there are algorithms to find square and cube roots)), or by factoring?
*December 9, 2014*

**matha**

Length of minute hand: 9m Angle moved in one hour = 360° Distance = (360/360)*2*π*9m=18π m Length of hour hand: 9m*2/3=6m Angle moved in one hour = 360/12=30° Distance = (30/360)*2*π*6 = π m Calculate the difference.
*December 9, 2014*

**calc**

This is a problem where the paraboloid projects a circle of radius 1 (represented by the region D) on the x-z plane. y=0 when x=z=0 y=1 when x²+z²=1 So let I=∫∫DydS It may be changed to cylindrical coordinates where dS=rdrdθ, and using y=x²+z²...
*December 2, 2014*

**Chemestry**

Density=mass/volume, so Volume = mass/density Check carefully units and number of significant figures.
*December 2, 2014*

**Statistics**

The "68-95-99.7 rule" represents the two-tail probability of data within ±1,2 and 3 standard deviations respectively. For example, the probability of picking a value X from a normal distribution within the range μ-σ<Xμ+σ is approximately 68%. ...
*December 2, 2014*

**MATHS - ratios**

use ratios: 60 km / 1.5 hours = 100 km /x hours x=1.5 hours * (100/60) = ?
*December 2, 2014*

**3rd grade math**

subtract each number from the next number, and make your guess from there!
*December 2, 2014*

**math**

P=2πsqrt(L/g) dP/dL = 2π(1/2)L^(-1/2)/sqrt(g) =2πsqrt(L/g)/(2L) transpose appropriate terms: 2*[dP/(2πsqrt(L/g))] = [dL/(L)] Each term in square brackets is equal to the fractional form of percentage error, thus proved. (use Δ => differentials instead of ...
*December 2, 2014*

**math help!**

Add -2-2w to each side to get w=10. Put w=10 back into each side of the original equation to verify that you get the same value on each side (=32).
*December 2, 2014*

**Ashworth college**

I believe the "68-95-99.7 rule" means the percentage of observations within 1-2-3 standard deviations from the mean. Try to apply the rule to answer the given question.
*December 2, 2014*

**physics**

This problem is similar to the previous. Again, use conservation of energies.
*December 2, 2014*

**physics**

Since friction is negligible, use conservation of potential and kinetic energies. KE (at bottom) => PE (at top) mv²/2 = mg*Lsin(θ) v=2,g=9.81,sin(θ)=1/2 Solve for L. I get 0.82m
*December 2, 2014*

**Physics**

Ideas: Conservation of energies also means: - energies are transformed from one form to another. Some are easier to exploit/recuperate than others. - total energy in universe is constant, but could be out of reach.
*December 2, 2014*

**Probability and Linear Math**

40% of total investment = 40%*500000 = 200000 This puts a ceiling on B, and a lower bound on A.
*December 1, 2014*

**physics**

Let A=30 kg boy B=40 kg boy Force = 50 N For boy A: Static Friction = mgμs=30*9.8*0.15=44.1N < 50N => Boy A is set in motion. Net force after kinetic friction = 50N-30*9.8*0.1N=5.9N Acceleration = F/m = 5.9/30=0.69 m/s² (backwards) For B, the 40kg boy Static ...
*November 30, 2014*

**Math**

What you'll need to do is 1. find the 3 intersections of the lines, which are then the vertices, (xa,ya), (xb,yb), (xc,yc). 2. Find the mid-points of each side using Mab=((xa+xb)/2, (ya+yb)/2), ... 3. Find the perpendicular bisector of each side by passing a line ...
*November 30, 2014*

**Chemistry Correction**

Correct, you should get 1.974*10^(-29) instead. If you do not get the above value, it could be: 1. you did not use the correct value of pi (such as 3.14, 22/7,...) 2. Your expression is missing many parentheses. Remember PEDMAS or PEMDAS which your calculator sticks to, but it...
*November 30, 2014*

**Please answer**

Here the population variance is not known, so use student-t distribution. A 95% (two-tail) confidence interval would include the limits. The value 1.96 comes from a T-value for 97.5% (half tail). x̄-Ts ≤ μ ≤ x̄+Ts where x̄=sample mean s=sample variance...
*November 30, 2014*

**Statistics**

Using Binomial probability function, we are looking for: P(280≤X≤300) =Σ C(300,r)p^r*(1-p)^(300-r) for r=280, 281, ...300, and C(300,r)=300!/((300-r)!r!) =0.00896+0.01530+0.02474+0.03777+0.05427+...+0.00004+0.0000 =0.98992 Using normal approximation with continuity...
*November 30, 2014*

**chem**

pKa=-log10Ka =-log10(6.3*10-8) =7.2
*November 30, 2014*

**statistics**

It all goes back to the definition and application of α and p-value. Read: http://www.statsdirect.com/help/default.htm#basics/p_values.htm for a detailed explanation.
*November 28, 2014*

**Math**

I=kS/d² where I=illumination, k=proportional constant >0 S=source strength >0 d=distance One light source is S, and the other is 4S. Let d=distance from weaker source, then 11-d =distance from stronger source. We have illumination as a function of d I(d) = kS/d²...
*November 28, 2014*

**math**

200 questions, 2 marks for good answer, -1/2 marks for wrong answer. Ajay answered all questions. If he didn't give any wrong answer, he would have got 400 marks. Each wrong answer will set him off 2.5 marks. If he got 360, he got (400-360)/2.5=16 wrong, therefore 184 ...
*November 28, 2014*

**physics**

v0=2.7 (package was rising) x0=11 x1=0 a=-9.8 x1=x0+v1*t+(1/2)at² 0=11+(2.7)t+(1/2)(-9.8)t² Solve for t to get t=1.8 sec.
*November 27, 2014*

**algebra**

First observation: People either liked the skin cream (x of them) or didn't like the skin cream (100-x of them). "80% of the people who liked the new skin cream also liked the new lip balm" that makes 0.8x liked new lip balm. "50% of the people who did not ...
*November 27, 2014*

**Math**

First factor the denominator: x^3+x^2+x=x(x^2+x+1) Then assume constants A, B and C as follows: (-5x^2-8x-3)/(x^3+x^2+x) = A/x + (Bx+C)/(x^2+x+1) The steps are to find constants A, B and C (the solution) by adding together the right hand side and comparing coefficients of each...
*November 27, 2014*

**mathematics of investment**

12% simple interest p.a. equals 0.12/365 simple interest per day. Principal=P10000 interest per day = P10000*0.12/365 =P3.28767 /day Time it takes to reach P700(=P10700-P10000) = P700/(P3.28767) = 212.9 days rounded up to = 213 days
*November 27, 2014*

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