Posted by **Tom** on Monday, October 2, 2006 at 2:56pm.

Using the 4 step method fidn teh derivative of F(x) =1/(x^2)

1) I got /(x^2+2xh+h^2)

2)2xh+h^2/(x^2+2xh+h^2)(x^2)

3)2x+h/(x^2+2xh+h^2)(x^2)

4)1/x

I don't understand why I got this problem wrong on my test can you explain the correct way?

The second step is wrong, it should be lim h->0 [F(x+h)-F(x)]/h

So we should have

lim h->0 1/(x^2+2xh+h^2) - 1/x^2 =

lim h->0 [x^2 - (x^2+2xh+h^2)]/[h*(x^2+2xh+h^2)*x^2] =

lim h->0 -(2xh+h^2)/[h*(x^2+2xh+h^2)*x^2] =

lim h->0 -(2x+h)/[(x^2+2xh+h^2)*x^2] =

lim h->0 -(2x+h)/(x^4+2x^3h+x^2h^2) =

-2x/x^4 =

-2/x^3 = F'(x)

## Answer this Question

## Related Questions

- Maths - differentiate from first principles y=1/x^2 i get to this then i get ...
- Math - Find and Simplify. f(x) = 5 − x^2 a)f(x + h) − f(x) b)(f(x + ...
- Algebra - I dont understand how to do the folliwing problems. Find and simplify ...
- Algebra - I dont understand how to do the folliwing problems. Find and simplify ...
- calculus - Difference Quotient of x^2-2x (x+h)^2-2(x+h)-(x^2-2x) / h x^2+2xh+h^2...
- Math - How would you simplify (-x^2+2xh+h^2-2x-2h-2x^2+4x)/h ?
- Calculus - 1/a+1 + 1/a-1 I solved this out by multiplying the (a+1) by (a-1) and...
- AP Physics - can you please explain this to me... Were given this eqaution x = ...
- Calculus (Help) - Also I would like to know how to set this problem up in ...
- calculus - The equation of the function is: f(x)=4-2(x-6)^1/3, for x not equal ...

More Related Questions