x方+x-1=0 求2x方+2x+3
问题描述:
x方+x-1=0 求2x方+2x+3
答
x^2+x=1
2*x^4+2*x^3+2x+3
=2*x^2(x^2+x)+2x+3
=2*x^2+2x+3
=2+3
=5