After simplification, you can get

(m^2- 1)x^2+(2-2m)x=- 1-m^3

As you can see,

When m= 1, 0=0, which is an identity, not a quadratic equation.

When m=- 1 and 4x=2, which is a linear equation with one variable, not a quadratic equation with one variable?

19、

A is the root of the equation x 2-x- 1

a^2-a- 1=0

a^2=a+ 1

a^4-3a-2

=(a^2)^2-3a-2

=(a+ 1)^2-3a-2

=a^2+2a+ 1-3a-2

=a^2-a-2

=0