f(x) at x0f(x0+y) - f(x0) = ay +by^2f'(x) = lim(y->0) (f(x+y) -f(x))/ yf'(x0)=lim(y->0) (f(x0+y) -f(x0))/ y =lim(y->0) (a+by) =aAns: C: f'(x0) =a
