Which description matches the transformations y=cosx undergoes to produce y=3cos (-2x)

Let us check the transformations. The first step is regarding the argument of the function, the - 2x part. So, first of all, the minus sign implies that the function is reflected along the y-axis since f (x) is replaced with f (-x). However, cosx is symmetric along that axis so there is no change on the graph. Also, the 2 factor means that the function is compressed along the x-axis, since now f (2) corresponds to f (1) etc. (if we substitute 1 in the cos (2x), it is as if substituting 2 in the origninal function cosx). Finally, we have that the factor 3 in front of cos, implies that the function is dilated along the y-axis; the highs become 3 times higher and the lows 3 times low.