Problem Solving

gmat_perfect wrote:What is the value of X if 3^(2x-2)-5*3^(x-2)-66 =0?

A. 2
B. 3
C. 4
D. 5
E. 6

Another approach:
Now 3^(2x-2) = 9^(x-1) = 5 * 3^(x-2) + 66.
Note that 5 * 3^(x-2) always ends in 5 because 3^(x-2) is odd.
Or 5 * 3^(x-2) + 66 ends in last digit of 5 + 6 which is 1.
Or 9^(x-1) ends in 1.
So (x-1) is even.
Or x is odd.
Next, check between x =3 and x = 5.
We will get that x = 3 satisfies the equation.