Posted by **rocky** on Wednesday, September 18, 2013 at 8:54pm.

I've tried to simplify this a million different ways, but I can't seem to get the right answer. Please help.

((1/(x+h)^3)-(1/x^3))/8h

- Pre-Calculus -
**Reiny**, Wednesday, September 18, 2013 at 10:44pm
Well, try 1,000,001 times.

((1/(x+h)^3)-(1/x^3))/8h

= [ (x^3 - (x+h)^3)/(x^3(x+h)^3) ]/(8h)

= [ ( x^3 - x^3 - 3x^2h - 3xh^2 - h^3)/(x^3(x+h)^3]/)8h)

= [ (-3x^2 h - 3xh^2 - h^3)/(x^3(x-h)^3 ]/(8h)

divide top and bottom by h

= [-3x^2 - 3xh - h^2)/(x^3(x-h)]/8

usually this is a limit question, where h ---> 0

in that case this would reduce to

[-3x^2/x^4]/8

= (-3/8)/x^2

## Answer this Question

## Related Questions

- Math - 2x(5*2-3) > x(3-5)-2(x-1) the answer I have got is x > 2/18. Can ...
- calculus - I've tried this problem about 20 times and a bunch of different ways ...
- Pre Calculus - So I only have 3 homework questions left and I can't seem to ...
- algebra - I have tried this problems all ways please help simplify 5[-8-(34-49...
- Calculus - Use integration by parts to find the integral. Round the answer to ...
- physics - Find the final velocity of the two balls if the ball with velocity v2i...
- Chemistry - Find the pH of mixture of acids. 0.185 M in HCHO2 and 0.225 M in ...
- pre-calculus - im having trouble finding a general solution for sin2x+sinx=0 all...
- Physics - Two masses, m1=3kg and m2=2kg, are suspended with a massless rope over...
- Pre Calculus - Simplify 2(3-i^14)- (5-i^23) 3-i Simplify: (5-3i)^2 16+30i ...