Thursday
December 18, 2014

Posts by Steve


Total # Posts: 27,588

Calculus
f(x) = √(x^3+4x) f'(x) = (3x^2+4) / 2√(x^3+4x) f'(2) = 16/8 = 2 So, now you have a point and a slope. The line is y-4 = 2(x-2) y = 2x See the graphs at http://www.wolframalpha.com/input/?i=plot+y%3D%E2%88%9A%28x^3%2B4x%29%2C+y%3D2x+for+x%3D-1..3
November 14, 2014

math
32/100 That can, of course, be reduced as desired.
November 14, 2014

sixth grade math
do you mean 24% ? If so, then 360 = .24x x = 360/.24 = 1500
November 14, 2014

sixth grade math
I'm having trouble with the English: What is the "of" doing there?
November 13, 2014

Calculus Please Help
F(x,y) = e^(2x+y) Fx = 2e^(2x+y) Fy = e^(2x+y) Fx(1,-1) = 2e^(2-1) = 2e Fy(1,-1) = e^(2-1) = e F(x, y, z) = xy + xz -yz Fx = y+z Fy = x-z Fz = x-y Fx(0,-1,1) = 0 Fy(0,-1,1) = -1 Fz(0,-1,1) = 1 F(x,y,z) = 2x^0.2 y^0.8 + z^2 Fx = 0.4x^-0.8 y^0.8 Fy = 1.6x^0.2 y^-0.2 Fz = 2z Fx(0...
November 13, 2014

Math
multiply top and bottom by -9-9i, Note that (-9+9i)(-9-9i) = 9^2+9^2 = 162 So, you have (-10-6i)(-9-9i)/162 Now just do the multiplication and put into standard form.
November 13, 2014

Trigonometry
well, just plug in the numbers: cot x = (3.5)(9.8)/5.4^2
November 13, 2014

Algebra
(a) f and g are both degree 4, so their sum cannot be of higher degree. (b) 1/2 g(x) = x^4-3x^2+x - 1/2 f - 1/2 g = -x + 5/2 Looks like 1 is the smallest possible degree.
November 13, 2014

Math
You might take all 6 red balls, all 5 green balls first. So, you might have to take out 6+5+3=14 balls to be sure you also have 3 yellows. Extra credit: how many do you need to be sure you have 3 balls of some color? Hint: There are 3 colors.
November 13, 2014

Math
Thanks alot Reiny that was super helpful. I have a math test tomrrow!
November 13, 2014

Math
I'm sorry but this does not help. WHat is D?
November 13, 2014

Math
Can anyone show me how to solve this? .1g+3.75m=7.36 and 8.2g+21m=73 Thank you
November 13, 2014

Math help please!!!!!!
correct again
November 13, 2014

Math (PLEASE!)
But you are right. D is also true.
November 13, 2014

Math (PLEASE!)
well, 11 is greater than 10.7 11 > 10.7 11.1 is even greater 11.1 > 11 > 10.7 Can you use the number line? If, plot all those values. The ones on the right are greater than those to their left.
November 13, 2014

Math (PLEASE!)
I like C
November 13, 2014

Math help please!!!!!!
correct
November 13, 2014

Algebra
I get -15 6x^3*4 + 4x^2*3x + -7x*3x^2 + -5*6x^3 24+12-21-30 = -15
November 13, 2014

Algebra
h(x) = (3x^2-5x+3)-(9x^3-3x+1) so, just subtract tghe coefficients of like powers.
November 13, 2014

math take 2
fcator out 4tan^2θ to get 4tan^2θ(2sinθ+1) = 0 so, tanθ = 0 or sinθ = -1/2 θ=0 or θ = 7π/6 or θ = 11π/6 You didn't specify the domain, so I'll let you worry about that. If you want all solutions, then that would be &#...
November 13, 2014

math
fcator out 4tan^2θ to get 4tan^2θ(2sinθ+1) = 0 so, tanθ = 0 or sinθ = -1/2 θ=0 or θ = -π/6 You didn't specify the domain, so I'll let you worry about that. If you want all solutions, then that would be θ = πn θ...
November 13, 2014

science
the same
November 13, 2014

Math *checking answers*?
Nope - my bad. B,C,D are all the same You want 9.5/3 = x/7 but B,C,D are all 9.5/3 = 7/x
November 13, 2014

Math *checking answers*?
I like C for #2. It's the same as 9.5/3 = x/7
November 13, 2014

calc
I think you want g(x) = 3x√(x+5) on [-5,0] g(-5) = 0 g(0) = 0 So, we want c somewhere in (-5,0) such that f'(c) = 0 f'(x) = 3(3x+10) / 2√(x+5) f' = 0 when 3x+10 = 0 So, c = -10/3 which is in the domain.
November 13, 2014

calc
In that case, g(0) = 0 g(5) = 15√10 Again Rolle's Theorem does not apply. Try again.
November 13, 2014

calc - eh?
g(0) is not defined, since sqrt(-5) is not real. So, g(x) does not satisfy the condition that g(0) = 0 You want to reconsider any part of the question?
November 13, 2014

MATH HELP PLEASE
(13/4)(2x + 3/4) (13/4)(2x) + 13/4 * 3/4 (13/2)x + 39/16
November 13, 2014

Math: Chi Squared
Boy, you don't give much context, do you?
November 13, 2014

Intermediate Algebra
clearly the domain is not (-oo,100) negative percent makes no sense. I'd say the domain is [0,100) C(X) -> oo as x->100, meaning that the harder you try to squeeze out that last bit of pollution, the morse it costs. So, just evaluate C(90). Then double that, since we...
November 13, 2014

Algebra
-3x^5 + 24x^2 factor out -3x^2 and you have (-3x^2)(x^3) + (-3x^2)(-8) -3x^2 (x^3-8) Now recall the factorization of the difference of two cubes, and you have -3x^2(x-2)(x^2+2x+4)
November 13, 2014

Science
F = ma so, a = F/m the x-component is F cos60° and sine for y
November 13, 2014

Molecular Calculations
convert g of Sn to moles. You will need that many moles of O2. Then find the mass for that many moles of O2.
November 13, 2014

Algebra 2
7x^2 = 21x 7x^2-21x = 0 7x(x-3) = 0 This is why we always set stuff to zero. If the product of factors is zero, one of the factors must be zero. So, we have 7=0: never x=0: x=0 x-3 = 0: x=3 Those are the solutions: x = 0 or 3
November 13, 2014

math
0.8 = 8/9 So, you have 10.1 + 8/90 = 101/10 + 8/90 = 917/90
November 13, 2014

Calculus
yes
November 12, 2014

math
at any depth y, the radius of the surface of the water is y/2. So, v = pi/3 (y/2)^2 y = pi/12 y^3 dv/dt = pi/4 y^2 dy/dt Now plug in your numbers.
November 12, 2014

Calculus - PLEASE HELP!!
Looks good to me
November 12, 2014

math
(6.0-0.3)/4
November 12, 2014

Inverses of functions
f^-1(a-1) = -3 a-1 = f(-3) a-1 = 2 a = 3 Not sure just what you're asking
November 12, 2014

math
b/g = 8/5 b = g+135 now just solve for g
November 12, 2014

Pre-Calculus
Look what happens when x gets huge. The equation is basically 5y^2 = 20x^2 y^2 = 4x^2 so the slopes are 2 and -2
November 12, 2014

Math
x-25.6 = 84.3
November 12, 2014

Math
m-4=11 m+u=53 now just find u
November 12, 2014

Math
(100-50)/(3-1.5)
November 12, 2014

Science
you are correct
November 12, 2014

math
s=m m = 4(s-18) Each had 24
November 12, 2014

Pre-Calc/Trig
range is all positive >2, as well as all negative On the interval (-1,1) the numerator is positive and the denominator is negative.
November 12, 2014

Math HELP!
x-10 = 47 x-25.6 = 84.3
November 12, 2014

Algebra HELP!
If the population is P, then 14/50 * P = 30
November 12, 2014

Math - eh?
eh? try that in English
November 12, 2014

Arithmetic Progression
a + a+d = 4 a+9d = 19 a=1 d=2 So, now add T5 and T6
November 12, 2014

Algebra
the two roots have product c and sum 7 Since the coefficient of x is 1, all the rational roots are integers. (x-1)(x-6) = x^2-7x+6 (x-2)(x-5) = x^2-7x+10 ... I think you can see that there are only a few values for c.
November 12, 2014

Calculus
∫v(v^3+5)^2 dv = ∫v(v^6 + 10v^3 + 25) dv = ∫v^7 + 10v^4 + 25v Now just integrate each term.
November 12, 2014

caculus
f"(x) = -4sin(2x) f'(x) = 2cos(2x) + c1 f(x) = sin(2x) + c1*x + c2 Now plug in the initial conditions to find c1 and c2
November 12, 2014

calculus
a(t) = 36t+10 v(t) = 18t^2+10t+c v(0)=9, so c=9 and v(t) = 18t^2+10t+9 s(t) = 6t^3+5t^2+9t+c s(0) = 16, so c=16 and s(t) = 6t^3+5t^2+9t+16 So, find s(11)
November 12, 2014

Calculus
Try this site: http://mathworld.wolfram.com/RiemannSum.html
November 12, 2014

alg 2
think back to algebra I. The QF is x = [-b +/- sqrt(b^2-4a)]/2a So, just plug in your number. The first is x = [-4 +/- sqrt(16-4(1)(-2)]/2 = [-4 +/- sqrt(16+8)]/2 = -4 +/- sqrt(24)]/2 = -2 +/- sqrt(6) Do the same with the others. First step is to get everything on the left ...
November 12, 2014

Algebra 2 HELP plz
t=2 is the correct time. So, plug in t=2 for your formula for h to get the max height. to see when it hits the ground, just set h=0: -16t^2+64t+80 = 0 -16(t+1)(t-5) = 0 so, h=0 at t=5
November 12, 2014

Pre-Calc/Trig...
2(x+5)/(x-3)
November 12, 2014

College Algebra
This is just a parabola, with its vertex at h = -b/2a, or in this case h = 3.817/0.14
November 12, 2014

Math
w(3w-5) = 12 ...
November 12, 2014

College Algebra
y = a(x+2)(x-8) The vertex is midway between the roots, at x=3, so y(3) = 5 a(5)(-5) = 5 a = -1/5 y = -1/5 (x+2)(x-8) See http://www.wolframalpha.com/input/?i=-1%2F5+%28x%2B2%29%28x-8%29
November 12, 2014

College Algebra
usually college algebra students haven't learned about derivatives. However, s(t) is just a parabola, with its vertex at t = 112/32 so, plug that into s(t) to find the max height Note that you got your derivative wrong, anyway.
November 12, 2014

algebra
if x at 2%, then the rest (10000-x) at 5%. So, 10000-x = 3x so solve for x, and the interest earned is .02x + .10(3x) = ?
November 12, 2014

algebra
y = ab^x a*b^2 = 3 a*b^9 = 33 a = 3/b^2, so a*b^9 = 3/b^2 * b^9 = 3b^7 = 33 b = 11^(1/7) a = 3/11^(2/7) y = 3/11^(2/7) * 11^(x/7) = 3*11^((x-2)/7) y(15) = 3*11^(13/7) = k
November 12, 2014

math olympiad
there are many such rectangles. 1 x √88 2 x √85 ... √44 x √45
November 12, 2014

intermediate algebra
the line through (2,3) and (2,0) is x = 2 That is a vertical line. So, the perpendicular line through (2,3) is y = 3
November 12, 2014

Maths
h/10 = 1.8/1.2
November 12, 2014

St Ans School
75-x = x-45 ...
November 12, 2014

Math
How about writing that as 3x - 8y - 4 = 0
November 12, 2014

Math Help
ln√x-8=5 ln√x=13 √x = e^13 x = e^26 log2x+log2(x+2)=log2(x+6) log2(x(x+2)) = log2(x+6) x(x+2) = x+6 x^2+2x = x+6 x^2+x-6 = 0 (x-2)(x+3) = 0 x = 2 or -3 But, log2(x) is not defined for x <= 0, so x=2 is the only solution check: log2(2)+log2(2+2) = log2(2+6...
November 12, 2014

Math
if course not "all reals" plug in just some value and see whether the equation balances. In particular, try x=0: log(4) =?= log(2) I don't think so. What you need to realize is that if 2^x = 2^y or log2(x) = log2(y) or 2x = 2y or 2+x = 2+y or in general, for any ...
November 12, 2014

Maths
1.3/1.8 = h/(7+1.8)
November 12, 2014

Math
you want e^.12x = 3
November 12, 2014

maths
a:b = 3:5 = 12:20 b:c = 4:7 = 20:35 a:b:c = 12:20:35
November 12, 2014

math algebra
Hard to tell, but it appears that you have (x-3)/4 - (y-2)/5 = -1/4 (4-x)/3 + (3-y)/2 = -13/20 which is the same as 5x - 4y = 2 20x + 30y = 209 20x-16y = 8 20x+30y = 209 46y = 201 so, x = 448/115 y = 201/46 Hmmm. Maybe you had x - 3/4 - y - 2/5 = -1/4 4 - x/3 + 3 - y/2 = -13/...
November 12, 2014

Pre-Calculus
recall that cos 2x = cos^2 x - sin^2 x
November 12, 2014

Pre-Calculus
7/12 = 1/3 + 1/4 now review your addition formula for tan(x+y)
November 12, 2014

Pre-Calculus
recall that cos(x-y) = cosxcosy+sinxsiny hence the name cosine -- sine of complementary angle
November 12, 2014

maths
we need (1+x)(0.9) = 1.08 x = 0.20 = 20% check: on $1.00 cost, mark up to $1.20 discount = $0.12, so the final price is $1.08, or 8% profit
November 12, 2014

Pre-Calculus
cos(cos^2+sin^2) don't forget your Algebra I now that you're taking trig!
November 12, 2014

Math
surely the explanation in your text will be more thorough than any offered here. Also, google is your friend...
November 12, 2014

Geometry
s = rθ, so θ = s/r
November 11, 2014

math
12 and 15
November 11, 2014

math
yes, you did
November 11, 2014

Calculus
just use the power rule: d/dx(x^n) = n x^(n-1) so, f'(x) = 3x^2 + 5/x^2
November 11, 2014

Geometry
No, it's November 11. I think you need to provide a little more context. p -> q where p=It's snowing today and q=It is December
November 11, 2014

math
Assuming that's $2.90 each, then 2*2.9 = 5.80 So, now, which has cost more for two packs of batteries?
November 11, 2014

calculus related rates
PV = k V dP/dt + P dV/dt = 0 dP/dt = -(P/V) dV/dt Now just plug in your numbers. By the way, this is true only if the temperature remains constant. More generally, PV = kT
November 11, 2014

calculus inverted cone
when the contents have depth y, the radius of the surface of the liquid is y/2 So, v = pi/3 r^2 y = pi/3 (y/2)^2 y = pi/12 y^3 dv/dt = pi/4 r^2 dy/dt Now just plug in your numbers.
November 11, 2014

Math
e+s = 80 e-17 = 2(2/3 s) Now just solve for e and s, and then get e-s.
November 11, 2014

Math
looks ok. But that depends on what x represents...
November 11, 2014

Math
9^2+35
November 11, 2014

Math
5 * 50/(5+8+7) = 12.5 m
November 11, 2014

College Algebra
there are lots of good graphing sites. Try here: http://www.wolframalpha.com/input/?i=plot+y%3D1%2F2x-3 The two equations describe the same line.
November 11, 2014

Advanced Algebra
3x=4(4-2x)=11 I suspect a typo
November 11, 2014

Pre-Calc/Trig
extrema where 12x^2 - 24x = 0 12x(x-2) = 0 Now apply the 2nd derivative test, and what you know about the general shape of cubics.
November 11, 2014

math
I suspect that V = XYZ So, just multiply the three values
November 11, 2014

Calculus
Go to http://www.wolframalpha.com/input/?i=8ln%28sec%28x%29%29+ and scroll down a bit.
November 11, 2014

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