求解一次函數題目 !!!

y = (m^2 - m)x^(m^2 - 3m + 1) + m - 3 是一次函數，則
m^2 - 3m + 1 = 1 及 m^2 - m =/= 0
m^2 - 3m = 0 及 (m =/= 0 或 1)
(m = 0 或 m = 3) 及 (m =/= 0 或 1)
所以 m = 3

For the function to be of degree 1(一次 函數), the power of x must be 1.
The power of x^(m^2 - 3m + 1) must be equal to 1.
That is m^2 - 3m + 1 = 1
m^2 - 3m = 0
m(m - 3) = 0
m = 0 or 3.
m = 0 is rejected because the coefficient (m^2 - m) will then be 0.
so m = 3.