Wednesday
November 26, 2014

Posts by Steve


Total # Posts: 27,019

College algebra
f(x) has 3 changes, so 3 or 1 + roots f(-x) has no sign changes, so no - roots check: http://www.wolframalpha.com/input/?i=6x^5-6x^4%2B7x^3-8
November 9, 2014

consumer math
799.99(1-0.40) = 479.99 or, $480
November 9, 2014

calculus
y = log |2-x| y' = 1/|2-x| (-1) = 1/(x-2)
November 9, 2014

Pre-trig/Calc
1 positive, 2 or 0 negative check: http://www.wolframalpha.com/input/?i=x^3%2B3x^2-18x-40
November 9, 2014

Math
start with x. The value after each step is listed below x 2x 2x+6 (2x+6)/2 = x+3 x+3-3 = x you always get your original number.
November 9, 2014

calculus
s = t^9 ln|t| s' = 9t^8 ln|t| + t^9/t = t^8(9ln|t| + 1)
November 9, 2014

Math
15.3g + 2q + 3.79 Note that you don't need an equation, just an expression
November 9, 2014

calculus
y' = (26x^2-26)e^-3x - 3(13x^2-26x+26)e^-3x = -13(3x^2-8x+8)e^-3x
November 9, 2014

Math
#1 False A triangle has three angles, which add up to 180 degrees. The two right angles use all that up. #2 True #3 True #4 False Just draw any obtuse triangle. If two of the legs happen to be equal, stretch one of them a little. #5 True #6 False. Draw a tall skinny isosceles ...
November 9, 2014

Math -word problem
Consider the room. The front wall is square ABCD, and the back wall is EFGH. The front outlet (P) is a foot from the floor (AB), and the back outlet (Q) is a foot from the ceiling (GH). A line directly up and across and down is 20 feet. But, you can do the following: Unfold ...
November 9, 2014

calculus
just use the product rule and chain rule: y = uv y' = u'v + uv' where u=(2x+1)^3 v=(4x+1)^-4 y' = 3(2x+1)^2(2)*(4x+1)^-4 + (2x+1)^3*(-4)(4x+1)^-5(4) = -2(2x+1)^2(4x+5) --------------------- (4x+1)^5
November 9, 2014

math pre algebra
how about 5x+7y
November 9, 2014

Algebra 2
plug in your coefficients at http://www.gregthatcher.com/Mathematics/GaussJordan.aspx to see all the details Or, you can try this: http://www.wolframalpha.com/input/?i=solve+{{3%2C4%2C1}%2C{1%2C3%2C-2}%2C{-2%2C1%2C-2}}*{{x}%2C{y}%2C{z}}%3D{{1}%2C{-2}%2C{-5}}
November 9, 2014

Algebra 2
(2x-1)^2 = x^2 + 33 4x^2-4x+1 = x^2+33 3x^2-4x-32 = 0 (3x+8)(x-4) = 0 ...
November 9, 2014

math
315 = 3^2 5 7 882 = 2 3^2 7^2 So, GCF = 3^2 7 = 63
November 9, 2014

math count warm up
just start writing down the facts. If the 4 digits, left to right are a,b,c,d, then: a+b=c b+c=d c+d=10a+b a+b=c d-b=c 10a+b-d=c a+b=d-b a+2b = d 10a+b-(a+2b) = a+b 8a = 2b b = 4a so, c=5a and, d=9a Since a,b,c,d are single digits, a must be 1. So, we get 1459
November 9, 2014

algebra
w(3w-2) = 16 w = 8/3 p = 2(8/3 + 6) = ?
November 9, 2014

math
6 - 4(2/3) = ?
November 9, 2014

projectives
time to hit: 4.9t^2 = 90 t = 4.29 s 4.29s * 50 m/s = 214.28 m
November 9, 2014

calculus
see related questions below
November 9, 2014

Math
Drop a perpendicular from G on CD to F. Now you have a rectangle GDEF with sides 3.5 and 4.5 Also, triangle CGF where CG = 3.5/√3 CF = 7.0/√3 Now the perimeter is easy - add up three sides of the rectangle, and the triangle.
November 8, 2014

math
I don't see any fractions If you meant (11+x)/(13+x) = 10/11 then x=9
November 8, 2014

Calculus
Do you mean ln√x or √lnx ?
November 8, 2014

trig
recall your sum of angles formula for tan recall that tan(180) = 0
November 8, 2014

Math Question
QR = 7.1 tan58° Area = (1/2)(PR)(QR)
November 8, 2014

math
your math is ok, freddy, but the spelling, not so much...
November 8, 2014

math
Hmmm. How can someone savvy enough to use a computer, not know what 1+1 is? I suspect either a test posting, or someone really bored.
November 8, 2014

Algebra 2
You always want to set things equal to zero: 6x^2-13x+6 = 0 Now, just have to have some practice factoring to get to (3x-2)(2x-3) = 0 Now, since if the product of two numbers is zero, one of the numbers must be zero. So, either 3x-2 = 0 and x = 2/3 or 2x-3 = 0 and x = 3/2 You ...
November 8, 2014

Calculus (math)
Draw a diagram, looking from the side. If the observer is at distance x, then The angle Ø from the eye to the bottom of the picture is such that tanØ = d/x The angle θ subtending the picture is tan(Ø+θ) = (d+h)/x We want to determine x for ...
November 8, 2014

math
(3x-2)/8 + (2-x)/ 4 = - 1/2 easy way: clear fractions by multiplying by 8: (3x-2) + 2(2-x) = (-1/2)(4) 3x-2+4-2x = -2 x+2 = -2 x = -6 check: (3(-6)-2)/8 + (2-(-6))/4 = -20/8 + 8/4 = -5/2 + 2 = -1/2
November 8, 2014

mathematics
a + a+2d = 12 (a)(a+d) = 24 a=4, d=2 check: 4,6,8,10,... 4+8=12 4*6=24
November 8, 2014

Mustapha
ever try google? Here's one discussion: http://www.meritnation.com/ask-answer/question/determine-the-oxidation-number-of-cr-in-k2cr2o7/redox-reactions/1515787
November 8, 2014

algebra
#1 If you mean f(n) = 3(n-3) then f(5) = 3(5-3) = 6 f(n) = 3^(n-3) then f(5) = 3^2 = 9 f(n) = 3^n - 3 then f(5) = 3^5-3 = 240 How did you come up with 279? #2 f(n) = 2f(n-1)+2 f(1) = 4 f(2) = 2(4)+2 = 10 f(3) = 2(10)+2 = 22 #3 f(n) = (4-n)/(n+3) f(3) = (4-3)/(3+3) = 1/6 #4 I ...
November 8, 2014

Maths
C = pi * d so, the turns is 44/C where C is in meters
November 8, 2014

math - typo
3:1:15 requires three quantities.
November 8, 2014

calculus
d/dx u^n = nu^(n-1) u' d/dx arctan(u) = 1/(1+u^2) u' d/dx ln(u) = 1/u u' So, we have y' = 2(3/2) √(22x+31) * (22) + 1/(1+(22x+21)) * (1/2) * 1/√(22x+21) * 22 + 1/(11x+16) * 11 - 22 = 66/√(22x+31) + 11/((22x+22)√(22x+21)) + 11/(11x+16) - 22
November 8, 2014

calculus
That would be 4(cos(6x-1) - 6xsin(6x-1)) ------------------------------ 3cos(3x) - 3 at x=0 that is 4(cos(-1)-0) ---------------- 3-3 -> -∞
November 8, 2014

Calculus
See the related questions below
November 8, 2014

Trig
Extend AB to meet the vertical from C at D. It is easy to determine that in triangle ABC ∠C = 47° ∠B = 88° Now just use the law of sines to get AB.
November 8, 2014

Intermediate Algebra
well, let's just assume that there is a t. After all, if there is none, the B is just a constant: 604.47 So, since polynomials are normally written in descending power order, I'd guess B = 18.75t + 585.72 So, you want to solve 18.75t + 585.72 > 1050 18.75t > 464....
November 8, 2014

Intermediate Algebra
B=18.75+585.72 where is the t?
November 8, 2014

Calculus (math)
See the related questions below
November 8, 2014

Math
cos is negative in QII, QIII You reference angle is 0.927 So, x = pi±0.927
November 8, 2014

calculus
V = IR dV/dt = R dI/dt + I dR/dt Now just plug in your numbers.
November 8, 2014

Calculus
I guess you should have checked my math. The actual formula for the volume is (π/3)((18+y)(3+y/6)^2-18*3^2) = π(y^3/108 + y^2/2 + 9y) because the water is in the bottom of the cone dv/dt = π/36(y+18)^2 dy/dt 4.9 = π/36*20^2 dy/dt dy/dt = .14 m/min or 14.0 ...
November 7, 2014

Calculus
When the water has depth y, the radius of the surface is 3 + (y/12)(5-3) = 3 + y/6 Its volume at that point is v = 1/3 (R^2-r^2) h = (1/3)((3+y/6)^2-3^2)y = y^3/108 + y^2/3 Now we are ready to begin. When y=2, v = 8/108 + 4/3 = 38/27 dv/dt = (y^2/36 + 2y/3) dy/dt 4.9 = (4/36...
November 7, 2014

Calculus (math)
as usual, draw a diagram. The distance z between the boats at time t hrs after 2:00 is z^2 = (15t)^2 + (20-20t)^2 2z dz/dt = 2(15t)(15) + 2(20-20t)(-20) z dz/dt = 1250t - 800 clearly dz/dt=0 when t=8/1250 hours Now just change that to a time of day.
November 7, 2014

AP CALC. AB
the .75 comes from the fact that the diameter is increasing 1t 1.5in/min. The radius is half that. and yes, he meant to solve for dh/dt, since that was the question asked. Part 1 just uses the fact that the volume of a box is length*width*height. can you say duh?
November 7, 2014

helpppppppp
7c+3d = 4m 1m = 1c+1d So, 4m = 4c+4d 7c+3d = 4c+4d 3c = d
November 7, 2014

BRAINMATH
If the family has b boys and g girls, b = g+4 So, b = (g-1)+5 so, each sister has 5 more brothers than sisters
November 7, 2014

Pre-Calc/Trig
numerator will be 1 or 2 denominator will be 1 or 3 all can be positive or negative
November 7, 2014

Math
cos pi/3 = 1/2 so, t = pi/3 That's the reference angle. cos is positive in QI and QIV, so the other solution is t = 2pi - pi/3
November 7, 2014

Physics
the vertical speed is 200 sin30 = 100 m/s So, the height is h(t) = 100t - 4.9t^2 As you recall from algebra I, the vertex of the parabola is at t = -b/2a, which in this case is 100/9.8 So, plug that in to get the max height. The ball is in the air twice that long, and you know...
November 7, 2014

Algebra
I'll do one, and you try the other. 2x^2+7x = 4 (x^2 + 7/2 x) = 2 (x^2 + 7/2 x + (7/4)^2) = 2 + (7/4)^2 (x + 7/4)^2 = 81/16 x + 7/4 = ±9/4 x = -7/4 ± 9/4 x = -4 or 1/2 Just recall that (x+a)^2 = x^2 + 2ax + a^2 That's why I added (7/4)^2 to both sides. ...
November 7, 2014

science Help 911!!
Looks good to me.
November 7, 2014

ALakh narayan sing high school Ekma saran
1/6(2x+3y)+x/3=8 1/2(7y-3x)-y=11 Rearranging things a bit to get rid of the bothersome fractions, we have 4x+3y = 48 -3x+5y = 22 Since y = (48-4x)/3, -3x+5(48-4x)/3 = 22 Or, -9x+240-20x = 66 29x = 174 x = 6 Now you can easily find y.
November 7, 2014

algebra - incomplete
I think you are missing a t in the formula.
November 7, 2014

multiplying integers
10^2 = 10*10 = 100 So, -10^2 = -100 Powers are done before multiplication. SO, the expressions is evaluated as -(10^2), NOT (-10)^2, which is (-10)(-10) = +100
November 7, 2014

algebra
no, it would never be positive. multiplying two negatives always gives a positive. That third negative then yields a negative product.
November 7, 2014

MATH
#1 -15 - (-5.6) = -9.4 #2 ...
November 6, 2014

Programming (Integer generator)
Ignoring the syntax error of the missing close brace, all you do is set the text to the latest string displayed. All the other strings are replaced. You need to append a new line for each value of i, not just do a clean reset of the text area each time.
November 6, 2014

algebra help!
The domain is the set of 1st values from the pairs: (b) In #2 you are correct.
November 6, 2014

Algebra
The slope of the line is 2, so y-a^2 = 2(x-a) y = 2x+(a^2-2a) 2(-3/2) + a^2-a = 0 a^2-a-2 = 0 2(0) + b^2-b = 3 b^2-b-3 = 0 Now you can find a and b, and pick the ones that work with the line.
November 6, 2014

Algebra
well, that would be where x^3-x^2+x+1 = x^3+x^2+x-1 2x^2-2 = 0 x = ±1 See http://www.wolframalpha.com/input/?i=solve+x^3-x^2%2Bx%2B1+%3D+%28+x^3%2Bx^2%2Bx-1%29
November 6, 2014

algebra
you have slope=3, so using the point-slope form, the line can be written as y-3 = 3(x-0) or, y = 3x+3
November 6, 2014

Calculus
If v is viewed as a piecewise linear function, then the slopes of the various segments are 154/7 = 21 (374-154)/(17-7) = 22 (418-374)/(19-17) = 22 (770-418)/(35-19) = 22 (1320-770)/(60-35) = 22 (1508-1320)/(64-60) = 47 (3905-1508)/(115-64) = 47 Looks like the 2nd stage kicked ...
November 6, 2014

Intermediate Algebra
If you are talking about powers, 9^(1/2) = 3 x^(1/2) = √x so you are talking about square roots. (-9)^(1/2) is not real, because negative numbers do not have real square roots. That is because if x = √(-9) then x^2 = -9. But all numbers are positive when squared.
November 6, 2014

Algebra help
ok ok v = 243 - 0.2s
November 6, 2014

Physics
Consider m3 to be at (0,0) m1 exerts its force at an angle of 30° m2 exerts its force at an angle of -30° As you say, each force is F=GMm/r^2 The resultant force will be at 0°, with a magnitude of F√3, the sum of the x-components of the two forces.
November 6, 2014

Calculus
y = (3x^2+2√x)/x = 3x + 2/√x y' = 3 - 1/x^3/2 You are correct
November 6, 2014

Trigonometry
secx = 2.1754 x = 0.4776 SInce secx is positive in QI and QIV, the other angle is 2π-0.4776 arcsin(2x) makes no sense, since x is an angle. That's if we are still referring to the first question. Now, in general, if sinθ = 2x, then cosθ = √(1-sin^2&#...
November 6, 2014

Trigonometry
c = 2πr, so one revolution of the plane travels 4π meters So, now we know that 5 min * 60s/min * 0.4rev/s * 4πm/rev = (5*60*4π)/(0.4) = 300π meters
November 6, 2014

Math
There is a good discussion of this problem at http://mathforum.org/library/drmath/view/65003.html This is, of course, a case involving Fermat's Last Theorem.
November 6, 2014

Math- Had Sub teacher, need help
apparently you stopped reading before finishing things. Read on past where it says So, the revenue will be ...
November 6, 2014

Math- Had Sub teacher, need help
revenue = rent * apts if there are x $7 increases, then we have rent = 294+7x units rented = 120-x So, the revenue will be (294+7x)(120-x) = -7x^2 + 546x + 35280 Recall that the vertex of a parabola is at x = -b/2a, which in this case is x = 546/14 = 39 So, with 39 rent ...
November 6, 2014

Algebra
recall that the vertex of a parabola is at x = -b/2a, which in this case is x = 1/.0064 = 156.25 so, just find f(156.25)
November 6, 2014

Math - incomplete
better explain some more about the diagram.
November 6, 2014

Math help!
m=r+4 m-10 = 3(r-10) Miriam is 16 and Ricardo is 12
November 6, 2014

Calculus
in that case, z^2 = (x+3)^2 + (5(x+3)/x)^2 z = (x+3)√(x^2+25) / x dz/dx = (x^3-75) / x^2√(x^2+25) and x = ∛75
November 6, 2014

Calculus
If the foot of the ladder is x feet from the fence, and it reaches to a height h on the wall, then using similar triangles, x/3 = (x+7)/h h = 3(x+7)/x the ladder's length z is z^2 = (x+7)^2 + h^2 = (x+7)^2 + (3(x+7)/x)^2 z = (x+7)√(x^2+9) / x So, for minimum z, we ...
November 6, 2014

CAL
#1 correct #2 is only partially complete f'(x) or df/dx y' or dy/dx
November 6, 2014

CAL
The _____________ of a function is a formula for the slope of the tangent line to that function at any point x. When the function is defined as f(x), the derivative will be written as __________or ________. When the function is written in the form of y =, the derivative is ...
November 6, 2014

Calculus
ohhh.. I think I know what I did wrong.. I did not even realize that I was doing something completely different
November 6, 2014

Calculus
wow - remember the chain rule if u = cos(x^4) then we have y = u^4 y' = 4u^3 u' y' = 4 cos^3(x^4) * (-sin(x^4)(4x^3) = -16x^3 sin(x^4) cos^3(x^4) y = sinx/(1+cos^2(x)) y' = [(cosx)(1+cos^2(x)) - (sinx)(2cosx)(-sinx)]/(1+cos^2(x))^2 y = sinx(sinx+cosx) y' = ...
November 6, 2014

Calculus
Find the derivatives of the following 18. y=〖cos〗^4 x^4 ANSWER: tanx2 19. y= sinx/(1+ 〖cos〗^2 x) ANSWER: 3sinx 20. y=sinx(sinx+cosx) ANSWER: sinx Can you check my answers?
November 6, 2014

Math Help
since loga + logb = log(ab) we have 4(ln(z(z+5)) = ln (z(z+5))^4 2ln(z-5) = ln (z-5)^2 Now, since loga - logb = log(a/b), we have ln ( (z(z+5))^4 / (z-5)^2 )
November 6, 2014

Calculus
Looks good to me. Nice work.
November 6, 2014

Calculus
3G 4H 5F 6B (though I never heard of such a term) 7E 8C 9A 10D Wow - either your order is mixed up, or you have some serious reviewing to do...
November 6, 2014

Calculus URGENT
f(x) = √x f(0) = 0 f(9) = 3 So, the slope of the secant is 1/3 f'(x) = 1 / 2√x So, we want to find c such that 1 / 2√c = 1/3 √c = 3/2 c = 9/4 So, c is in the interval [0,9] just to check, f(9/4) = 3/2 So, the equation of the tangent line at c is y...
November 6, 2014

Algebra 2
192x^2y + 72x^3 = 24x^2(8y+3x) 24rxy - 9rx^2 = 3rx(8y-3x) The only common factor I can see is 3x, so we have 3x(64xy+24x^2-8ry+3rx) Not sure just where you're trying to go with this Now, if the original had been without the parentheses, (192x^2y+72x^3)-24rxy-9rx^2 then we ...
November 6, 2014

matg
20 years is 4 half-lives, so there would be 300 * (1/2)^4
November 6, 2014

Science
PE = mgh = (45)(9.81)(2) J
November 6, 2014

Math
I get z(2.75,0) = 22
November 6, 2014

physics
recall your equation of motion. In this case, the height, as a function of t is h(t) = 2.54t - 4.9t^2 This is just a parabola, with the vertex at t = -b/2a = 2.54/9.8 = 0.26 So, just plug in t=0.26 to find the maximum height, h(0.26)
November 6, 2014

algebra
It's easy to construct such a polynomial with zeroes that are very difficult to find: 3x^5 - 12x^4 + 9x^3 + x^2 - 12 But, if you start out with the roots, it's easy to build the polynomial: (x-3)(2x+5)(3x-7)(x^2+4) = 6x^5 - 17x^4 - 14x^3 + 37x^2 - 152x + 420
November 6, 2014

geometry
draw a line mark point A. mark point B at a distance of 8.5 units away from A. Now, draw a circle of radius 6.2, with center at B. Point C can be anywhere on the circle just drawn.
November 6, 2014

Math
.815 = 815/1000 .021 = 21/1000 So, she added thusly: 5 815/1000 + 6 21/1000 = 11 876/1000 = 11 219/250
November 6, 2014

math
1.2 - (0.75 + 0.125 + 0.09) = 1.2 - 0.965 = 0.235
November 6, 2014

math
recall the slope-intercept form of a line: y = mx+b
November 6, 2014

Object Oriented Programming Concept Using C++
use how? R = 2T?
November 6, 2014

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