Saturday
April 19, 2014

Posts by steve


Total # Posts: 21,786

MATH VERY INCOMPLETE!!!!!!!!!!
Hmmph

Math
If you read carefully, I think you will find I did. 3 ways to choose the driver, 5! ways to arrange the riders.

Math
If you mean that the 6-person team must contain 3 drivers, then the driver can be selected in 3 different ways The remaining 5 riders can be arranged in P(5) = 5! ways If I have misread the problem, please clarify.

Calculus
or, u = 1-x^4 du = -4x^3 du so ∫(2x^3/√(1-x^4))dx = -1/2 ∫1/√u du = (-1/2)(2√u) = -√(1-x^4) Extra credit: Can you find the error in bobpursley's solution?

math
Looks like C to me can't mix x's and y's x^2*x^3 = x*x * x*x*x = x^5 but x^2 * y^3 = x*x * y*y*y

Math
Assuming you mean matrices and not determinants, take a look at http://www.wolframalpha.com/input/?i={{9%2C4}%2C{2%2C1}}+*+{{-9%2C-6}%2C{-1%2C-8}} The result is not one of your answers, so there's a typo somewhere. You can easily adjust the numbers on that web page, till t...

Calculus
I assume you meant fired straight up in the air. In that case, at time t seconds, the rocket has gone 2t miles. So, the distance D is found, as you showed, by D^2 = 9+y^2 = 9+4t^2 when the rocket is 4 miles up, t=2, and we have a 3-4-5 triangle, so D=5. 2D dD/dt = 8t when t=2,...

Algebra 9
2x^2-9x+4 = (2x-1)(x-4) 2x^2+14x+24 = 2(x+4)(x+3) so, what you have is x^2 / (2x-1)(x-4) * 4(x+1) / 2(x+4)(x+3) hm. no factors cancel but the 2's, so we wind up with 2x^2(x+1) / (2x-1)(x-4)(x+4)(x+3) = (2x^3 + 2x^2)/(2x^4+5x^3-35x^2-80x+48) Not very simple.

Calculus
your value x=2 is correct. a) yes, but v(25) represents the amount of fluid remaining after 25 minutes. It just happens also to be true that at that time the tank is empty. b) v(0) = 875 v(15) = 350 volume changed by -525 in 15 minutes, for an average rate of change of -525L/1...

Math
if the amounts are x,y,z for 6,7,8% respectively (in thousands), then we have x+y+z = 1200 z = x+y .06x + .07y + .08z = 88 x,y,z = 200,400,600

Calculus Help Please!!! Urgent!!!
-6x/y^5 is not the answer 3x^2 - 3y^2 y' = 0 now use the quotient rule: y" = (2xy^2 - 2x^2y y')/y^4 = 2x(y-xy')/y^3 = 2x(y-x(x^2/y^2))/y^3 = 2x(y^3-x^3)/y^5 or, use implicit differentiation twice: x^3-y^3 = 3 3x^2 - 3y^2 y' = 0 6x - 6y(y')^2 - 3y^2y&qu...

Math
-√60 = -√(4*15) = -√4√15 = -2√15

Algebra 2
there are 7 zeros in the first number, so it is 24*10^7 there are 4 leading zeros in the next number, so it is .24*10^-4 the denominator is .5*10^-2 Expressing each of those in scientific notation, where the number is between1 and 10, we have 2.4*10^8 * 2.4*10^-5 / 5.0*10^-3 =...

math
1/x = 1/3 + 1/6 x = 2 So, (B) Extra credit: how long does it take if all three work together?

math
13.3/3.2 * 72 = 299.25

math
Assuming the usual carelessness with parentheses, I read this as (10t-640)/t^2 = 0 a fraction is zero if the numerator is zero. So, 10t-640=0 t = 64 Now, if you meant 10t - (640/t^2) = 0 then clear the fraction and we have 10t^3 - 640 = 0 t^3 = 64 t = 4

algebra 2
The pay on the nth day is 2^(n-1) So,we want 2^(n-1) = 10000 n-1 = log10000/log2 n = 14.28 So, on the 15th day the pay is 2^14 = $163.84

algebra 2/trig
1/x + 1/8 = 1/3 x = 24/5

Algebra
5*x*x*(3x+5) divide up the factors any way you choose

algebra 2
256 + 2*256*.75 + ... + 2*256*.75^4 = 2*256(1-.75^5)/(1-.75) - 256 = 1306

algebra 2
In the nth year he makes 32000+300(n-1) so, when does that exceed 34700? 32000+300(n-1) > 34700 300(n-1) > 2700 n-1 > 9 n > 10

GEOMETRY
volume per cylinder: pi*9*8 = 226.19 2000/226.19 = 8.84

algebra 2
sigma upper limit 28 algebraic expression (8i-13) lower limit 1 index=i 28 ∑ 8i-13 i=1 You can see from the formula that the sum increases by 8 with each additional term (8i) The first term is 8*1-13 = -5 Now recall that the sum of the 1st n terms of an arithmetic sequen...

Calculus - amendment
just recall that the period of tan(t) is pi, not 2pi, so tan(2t) has period pi/2

math
if there were n pieces, you know that 1/6 n = 2 n = 12

Math
inequality sign is garbled. But P(n≠3) = 5/6

Calculus
no ideas? Try reading the theorem.

math
50 in^2 * (2.54cm/in)^2 = 322.58 cm^2 Note how the units cancel, leaving the desired units at the end.

math
since 832 >= 400, 832/400 > 1, and the 1st digit is in the hundreds position 217 < 700, but 217 >= 70, so 1st digit of quotient is in the tens position.

Math
both. vertical angles are congruent.

precal
Hi I know is is probably basic but can anyone assist with the following : Find all real Roots, expressing as whole # and # under radical sign, not as fraction. and factor completely f(x)= X^3-2x^2-15x+30 I got roots at 2 (x-2) and +/- √5 If someone solves and gets factor...

Calculus Help Please!!!
a I assume you can sketch graphs b yes f(0) = 0 and limit=0 from both sides c yes f'(0) = 1 and limit of f' = 1 from both sides

algebra
Im using this for trig functions ....so I cannot use fraction or decimal I have to simply use π. Im getting : π-3/2 (2)π-3/2 ***I don't know how to add 2π +(-3)? thank you for helping

algebra
No I mean how do you add them using common denominator? not using decimal or calculator

algebra
How do you add π -3/2?

ovarian and uterine cycles
Im sure this is in the book on this section.. but i think (not sure) FSH is 1.

Gr 10 math - finding vertices
whatever you do for one line, do for the other. If you have two points, they define a line.

algebra
can someone show line by line step by step factor x^2-15

Precalculus /Algebra
Hi I know is is probably basic but can anyone assist with the following : Find all real Roots, expressing as whole # and # under radical sign, not as fraction. and factor completely f(x)= X^3-2x^2-15x+30 I got roots at 2 (x-2) and +/- √5 If someone solves and gets factor...

math
Jamal writes the letters K-A-N-S-A-S on cards and then places the cards in a hat. What are the odds against picking an S?

alg.
recall that in the general quadratic, max y occurs at x = -b/2a. In this case, when t = 17/32. Just plug that in to get maximum h.

college alg.
recall that for the general quadratic, max y is at x = -b/2a. In this case, at t=7.1/9.8 Just plug that in to get s.

math multiple choice
13.75 + 55000(.60/200) = 178.75

Calculus - oops
oops --- y' = -y, so the tangent line is y-13 = -13(x-1) y = -13x+26 as shown at http://www.wolframalpha.com/input/?i=plot+y+%3D+e^%28x%2Barccos%28x-1%29%29%2Fx%2C+y%3D-13x%2B26

Calculus Help Please
when x=1, ln(y) - pi/2 = 1 y = e^(1+pi/2) at x=1, y' = -y so, now you have a point and a slope. y-e^(1+pi/2) = -e^(1+pi/2) (x-1) and convert that to slope-intercept.

Calculus Help Please
ln(xy) - cos^-1(x-1) = x 1/(xy) (y+xy') + 1/√(1-(x-1)^2) = 1 Now just solve for y'. You should get y' = y(1 - 1/x - 1/√(2x-x^2))

Calculus Help Please!!!
the normal line is perpendicular to the tangent line. Since the slope of the tangent line at x is y', find y'. 2x + 4y + 4xy' + 2yy' = 0 y' = -(2x+4y)/(4x+2y) = -(x+2y)/(2x+y) So, at (2,1) the tangent line has slope -4/5 Thus, the normal line has slope 5/4....

Math
D

college alg
well, just plug in your numbers and solve for t when the height is zero: -16t^2 + 184t = 0 just a good old quadratic equation.

Math
#2 f? x? I get 5f^2 + 11f - 2 #3 B #4 coefficients are the numbers multiplying the powers of x. So, B the final -3 is not a coefficient; it's just a constant.

Math
1A what did you get for the others?

physics
the man changed his velocity by 6.59 m/s in 3.92 ms, so his deceleration was a = 6.59m/s / 0.00659s = 1000m/s^2 and, since F = ma, the force should now be obvious.

maths Pls help trig
but oops: 25/√50 = 5/√2, not 1/√2

maths Pls help trig
the denominator is 50√50

PROGRAMMING
you can probably adapt this little perl ditty to your needs. Other languages may be more verbose, however. my %authors,%ages,%counts; while (<>) { last unless $_; my ($count,$age,$name) = split(/\s+/,$_,3); $authors{$name} = [$count,$age]; $ages{$age}++; $counts{$count}+...

Math
well, there's algebraic algebraically those are the only words I can think of right off where I can "form the word algebra". Git

Math
too late for your spelling and punctuation, apparently...

Math
well, it's clear that if there is 1 bus, the numbers work out: 40+16 = 36+20 If there are more buses, then since LCM(40,36) = 360, any multiple of 360 + 56 will also work, with an extra 9 buses if 40/bus, and an extra 10 buses if 36/bus, for each extra 360 kids.

Calculus Help Please!!!
just use the quotient rule: y" = (2xy^2 - 2x^2y y')/y^4 = 2x(y-xy')/y^3 = 2x(y-x(x^2/y^2))/y^3 = 2x(y^3-x^3)/y^5 or, use implicit differentiation twice: x^3-y^3 = 3 3x^2 - 3y^2 y' = 0 6x - 6y(y')^2 - 3y^2y" = 0 y^2 y" = 2x - 2y(y')^2 = 2(x -y...

math
x + x+30 = 90 now solve for x

pre calculus
y = 12-√x looks like a function to me, though the domain is restricted.

Math (help)
don't know what steps you want. The area of a cone is a = 2πr(r+s) just plug in the values for r and s

Math
correct since the legs are hypotenuse/√2, √6/√2 = √3 check: √3^2 + √3^2 = √6^2 3 + 3 = 6

Calculus Help Please!!! URGENT!!!!
A(t) = Ao * 2^(-t/5700) If you want that to use e instead of 2, then since 2 = e^ln2, A(t) = Ao * e^(-ln2/5700 * t) and k = ln2/5700. Now just plug in your numbers to answer the other questions.

calculas
if the box is all cardboard, and AB = 193 and h=2, then something doesn't add up, since the surface area is 4(A+B)+2AB

math
room: Vr = 11.35*9.5*8.3 = 894.9 box: Vb = 4.25*6.5*4.0 = 110.5 now, subtract and round.

Calculus Help
y = sin(π/√(θ^2+5)) weird, but just apply the rules y = sun(u) y' = cos(u) u' u = π/v u' = -π/v^2 v' v = √(θ^2+5) v' = θ/√(θ^2+5) put it all together and it spells MOTHER. Or, more mathematically, π&...

Calculus Help Please!!!
hmmm. well, I guess you can't use Taylor series either, eh? (sin2x)/(2x-tanx) I assume you've shown that lim (sinx)/x = 1, so if our limit is L, 1/L = (2x-tanx)/(sin2x) = (2x)/sin(2x) - tanx/sin2x = 1 - (sinx/cosx)/(2sinx cosx) = 1 - (1/cosx)/(2cosx) limit as x->0 i...

Calculus Help Please!!!
The key here is l'hospital's rule lim f/g = lim f'/g' so, the limit is the same as 2cos2x / (2 - sec^2 x) = 2*1/(2-1) = 2

Math
1n+7p = 5.55 3n+2p = 12.28 that's the same as 2n+14p = 11.10 21n+14p = 85.96 now subtract to get rid of the p's 19n = 74.86 n = 3.94

Geometry
Note that this is just a trapezoid with bases 3 and 8, and height 8. So, the area is (3+8)/2 * 8 = 44

Calculus
ok. If you mean (-1/3 t) - 1 then we have for the two tanks: Va = 48 - ∫16/5 dt = 48 - 16/5 t Vb = 48 - ∫1/3 t + 1 dt = 48 - t - 1/6 t^2 So, Va(5) = 48 - 16 = 32 Vb(5) = 48 - 5 - 25/6 = 38 5/6 Now just solve for when Va and Vb = 0 to find which drains first. If I s...

Calculus - eh?
Cannot parse -1/3t-1 Is that (-1/3)(t-1) or -1/(3t)-1 or -1/(3t-1)? none of those choices makes sense at t=0.

MATH ✿╣Check╠✿
looks good to me

Math
well, we have cosa = 12/13 sinb = 4/5 So, just plug them into cos(a+b) = cosa cosb - sina sinb

Calc2
well, we know that L{1} = 1/s and, we know from our handy table of transforms that L{t^n f(t)} = (-1)^n F(n)(s) so, L{t^2} = 2/s^3

MATH - Algebra
yes, except you had 22x, not 11x So, the answer is x^2 + 2x also, be sure to use parentheses to make it clear that you mean (11x^2+22x)/11 and not 11x^2 + (22x/11)

Algebra II -Please help
*whew* I had no idea how to apply the matrix to your calculations.

math
the two legs are a and b, and the hypotenuse is √(a^2+b^2). So, assuming a,b > 0, So, in QII, sin2x = b/√(a^2+b^2) cos2x = -a/√(a^2+b^2) sin^2(x) = (1-cos2x)/2 = (1+a/√(a^2+b^2))/2 = (a+√(a^2+b^2)) / 2√(a^2+b^2) and similarly for cosx

math
all those angles are the standard ones you should know. cot pi/3 = 1/√3 csc pi/3 = 2/√3 cos pi/4 = 1/√2 plug it in and you have (1/√3 + 2/√3)/(1/√2) = √6

Math
r/h = sin(a) v = 1/3 pi r^2 h = 1/3 pi h^3 sin(a)

Geometry
D

Dance Therapy
Best first step would be to talk to someone doing what you plan to do, and see what is best to study that is available, and where to pursue further education.

calculus I
gotta remember that v(t) = h'(t) = 24.5 - 9.8t now just plug in t=2 or 4

Calc 2
the 2nd one is just (3/2)^(k/2) so it of course diverges. so, what do you get for arctan?

math
how about .15 * 63.00 = ?

calculus
you do know that cos(z) = 0 when z is an odd multiple of pi/2, right? So, cos(2t) = 0 when 2t is an odd multiple of pi/2; that is, t is an odd multiple of pi/4. 45 degrees is an odd multiple of pi/4, right?

calculus
you have the product of three factors (2.5)(e^-t)(cos 2t) = 0 2.5 is never zero e^-t is never zero cos 2t = 0 when t = (2k+1)(pi/4) for integer k.

Discrete Math
just make your usual Venn diagram and start labeling the intersections.

Math
Thinking of the doubling rate, we can see that after t hours, the population is P(t) = 50 * 2^(2t) = 50*4^t So, we want 50*4^t = 1000000 4^t = 20000 t log4 = log 20000 t = log20000/log4 = 7.14 hours

advanced algebra
y = 10 - 2x

physics
5x10^6 rad/s = 795774 Hz Z = √(R^2 + (Xl-Xc)^2 Xc = 1/ωC = 1/(5*10^6 * 100*10^-12) = 1/(500*10^-6) = 2000 Xl = ωL = 5*10^6 * 100*10^-6 = 500 So, now you know R and Z. Go for it, and recall that I = E/Z

Math
since all dimensions are 1.6 times as big, the volume (multiplying all three dimensions) is increased y a factor of 1.6^3. 92 * 1.6^3 = ?

Calculus II
actually, Γ(n) = ∫[0,∞] x^(n-1) e^(-x) dx which is unusual, since n is usually used for constants. Usually it is written Γ(t) = ∫[0,∞] x^(t-1) e^(-x) dx As you probably should know, Γ(n) = (n-1)! for integer n. So, Γ(1) = 1 Γ(2)...

Calculus II
Using long division, we know that x^4(1-x)^4/(1+x^2) = x^6-4x^5+5x^4-4x^2+4 - 4/(x^2+1) So, the integral is just x^7/7 - 2x^6/3 + x^5 - 4x^3/3 + 4x - 4arctan(x) evaluated at 1 and 0, we have 1/7 - 2/3 + 1 - 4/3 + 4 - π = 22/7 - π now add π to that and you wind u...

math
cost is rate * distance. If the distance from home to A is x, then from home to B is 6-x. So, since the costs are the same, 50x = 75(6-x) 50x = 450-75x 125x = 450 x = 3.6 So, (C)

Math
there are only 3 colors, so the 4th sock must match one of the first three.

cape1 physics
thanks for the example.

Math/Physics
when Tyson left at 11:00, Rashad had already gone 200km, so the two were 580 km apart. They approached each other at 180 km/hr, meaning they met in 3 2/9 hours. So, by the time they met at 2:13:20, Tyson had gone 257.8 km.

Math
1000000 people/66000 mi^2 = 1000/66 people/mi^2 That's a lot less than any of the proposed densities, so (A) assuming the cited figures actually apply to Florida...

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