if we want to stretch graph vertically we need to multiply function f(x) with a number greater than 1. By doing so we will for same difference of x get larger difference of F(x) which means function will be stretched.
If we want to flipp over x axis function F(x) all we need to do is to multiply it by -1. Function will change its sign thus for same values of x we will get value of F(x) with oposite sign which means function will be flipped over x axis.
Looking at offered answers we can say that A and B arent answer because we didnt multiply function with number greater than 1.
Answer is C) G(x) = -4x^2
