Question

Find the difference quotient for f(x) = x2 + 4.

Answer 1

I am trying to simplify a difference quotient with the form

f(x+h)−f(h)/h

if f(x)=2/x2 I have attempted to cancel out the denominator of the numerator by the least common denominator method. I know that I can solve this using implicit differentiation, but am trying to use the difference quotient to get the partial derivative

Here is my work so far:

f(x+h)−f(x)(h)

=f(2/(x+h)2)−f(2/x2)h

=(2/(x+h)2)−(2/x2)h

here I multiply by the LCD

=(2(x2)−2(x+h)2)/(x2(x+h)2)h

Here I expand out the top and cancel out 2x2

=(2x2−(2x2+4xh+2h2))/(x2(x+h)2)h

=−(4xh+2h2)/(x2(x+h)2))h

Here I think I should multiply by 1/h to get rid of the h on the bottom

I end up with:

=4xh+2h2hx2(x+h)2

factor out an h

=−4x+2hx2(x+h)2