移项
x²=5x+1
则x³=x(x²)
=x(5x+1)
=5x²+x
=5(5x+1)+x
=26x+5
原式=2(26x+5)-5(5x+1)-27x+1
=52x+10-25x-5+27x+1
=6
已知：x^2-5x-1=0,求2x^3-5x^2-27x+1的值
移项
x²=5x+1
则x³=x(x²)
=x(5x+1)
=5x²+x
=5(5x+1)+x
=26x+5
原式=2(26x+5)-5(5x+1)-27x+1
=52x+10-25x-5+27x+1
=6