Question

已知x的平方加上x减1等于0,求x的平方加2x的平方加1等于几

Answer 1

x^2+x-1=0

x^2=1-x

是x^3+2x^2+1吧

=x*x^2+2x^2+1

=x[1-x]+2x^2+1

=x-x^2+2x^2+1

=x^2+x-1+2

=0+2

=2