for all numbers x and y, let f be a function such that f(x+y)=f(x)+f(y)-2xy and such that the limit f(x)/h=7
a. find f(0). Justify your answer.
b. Use the definition of the derivative to find the derivative of f(x)
c. Find f(x)
i already did section a and and got f(0) = 0, which my teacher said was correct. and i know that to get section c i would just take the integral of b. but i have absolutely no clue how to get b. would i just take the derivative of f(x+y)=f(x)+f(y)-2xy and set f(x+y) to 0? or do i take the derivative of