Question 1121107
The general quotient you are looking for is  with the added parentheses, {{{(f(x+h)-f(x))/h}}}.



You could start this way:


{{{f(x+h)=-1-(x+h)-2(x+h)^2}}}
{{{-1-x-h-2(x^2+2hx+h^2)}}}
{{{-1-x-h-2x^2-4hx-2h^2}}}


{{{AND}}}


{{{f(x)=-1-x-2x^2}}}



Now just put everything together according to your general quotient and simplify.