If the equation (m ^ 2-4) x ^ 3 + (m-2) x ^ MX + m + 1 = 0 is a quadratic equation with one variable, what is the value of M? (m^2-4)x^3+(m-2)x^2-mx+m+1=0

If the equation (m ^ 2-4) x ^ 3 + (m-2) x ^ MX + m + 1 = 0 is a quadratic equation with one variable, what is the value of M? (m^2-4)x^3+(m-2)x^2-mx+m+1=0

If the equation (m ^ 2-4) x ^ 3 + (m-2) x ^ MX + m + 1 = 0 is a quadratic equation with one variable
Should it be m ^ 2-4) x ^ 3 + (m-2) x ^ 2 + MX + m + 1 = 0
that
M ^ 2-4 = 0, M = 2 or - 2
M-2 is not equal to 0, M is not equal to 2
So m = - 2