Y - 6 = 10(x - 2) hope this helps :)
Take into account, that in general, a cosine function of amplitude A, period T and vertical translation b, can be written as follow:

In the given case, you have:
A = 4
T = 3π/4
b = -3
By replacing you obtain:

Hence, the answer is:
f(x) = 4cos(8/3 x) - 3
The literal equation for x = s=2r+3x
There no changes to the answer