Question

X的平方+X-1=0那么X的三次方+2X的平方-7等于多少 同上

Answer 1

x^2+x-1=0
x^2+x=1
x^3+2x^2-7
=x(x^2+x)+x^2-7
=x+x^2-7
=1-7
=-6