If the function f (x) = ax & # 178; + BX + 3A + B defined on [a-1,2a] is even, then a + B =?

If the function f (x) = ax & # 178; + BX + 3A + B defined on [a-1,2a] is even, then a + B =?

First of all, if f (x) = ax & # 178; + BX + 3A + B is even function, then the domain of definition must be symmetric about the origin, so A-1 = - 2A, so a = 1 / 3, then f (x) = 1 / 3x & # 178; + BX + 1 + B and f (- x) = f (x) has 1 / 3 (- x) &# 178; - BX + 1 + B = 1 / 3x & # 178; + BX + 1 + B is reduced to 2bx = 0, because x is a variable, it can only be reduced to B = 0