Let f(x)=-1-x-2x2, evaluate

Question

heres a picture for better view

Answer 1

f(x)=-1-x-2x².

f(x+h)=-1-(x+h)-2(x+h)²=

-1-x-h-2(x²+2xh+h²)=

-1-x-h-2x²-4xh-2h².

Now we subtract f(x), which is the same as adding 1+x+2x², giving us:

-h-4xh-2h². Divide by h: -1-4x-2h or -(1+4x+2h).