Tuesday
March 31, 2015

Posts by MathMate


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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