Express 9^(3x + 1) in the form 3^y , giving y in the form ax + b, where a and b are constants.

9^ (3x + 1)

We know that 3 to power of 2 equals 9.  3x3 = 3^2 = 9, 

= 3^ (2 * [3x + 1])

We simply the term because 2 * [3x + 1] = 6x + 2

= 3^ ( 6x + 2) 

This term is in the form of 3^ y, so we know that y = 6x + 2 by comparing like terms.

y = 6x + 2 a = 6, b = 2