Monotone increasing interval of function y = 2 ^ (- x + 3x-2)

Monotone increasing interval of function y = 2 ^ (- x + 3x-2)

It's y = 2 ^ (- x ^ 2 + 3x-2)
Let t = - x ^ 2 + 3x-2, then y = 2 ^ t is monotonically increasing on R
For t = - x ^ 2 + 3x-2, consider the axis of symmetry x = 3 / 2 of the quadratic function. Combined with the opening direction, we can know that the function is in X