Algebra

Anything to the power of 0 is 1, so if x = 0, 9^x would be 1. Lets assume x = 0. Then $(9^x - 2) \cdot (3^x + 1)$ would be equal to $-1 \cdot 1$ or -1. So, the minimum value of $(9^x - 2) \cdot (3^x + 1)$ is -1.