Question

已知x的平方+4x-1=0,求2x的四次方+8x的三次方-4x的平方-8x+1的值

Answer 1

x²+4x=1

所以原式=2x²(x²+4x)-4x²-8x+1

=2x²-4x²-8x+1

=-2x²-8x+1

=-2(x²+4x)+1

=-2+1

=-1