Question

已知x等于根号5-1求代数式x平方加5x-6的值

Answer 1

x=√5-1
x+1=√5
两边平方得x²+2x+1=5
即x²+2x=4
x²+5x-6=x²+2x+3x-6
=4+3(√5-1)-6
=4+3√5-3-6
=3√5-5