Question

已知X等于二分之根号五减一 求代数式二X的平方加X减一

Answer 1

已知X等于二分之根号五减一
x=(√5-1)/2
2x^2+x-1
=x(2x+1)-1
=[(√5-1)/2](√5-1+1)-1
=(5-√5)/2-1
=(3-√5)/2

Answer 2

x=(√5-1)/2
2x²+x-1
=2(x²+x/2)-1
=2(x²+x/2+1/16-1/16)-1
=2[(x+1/4)²-1/16]-1
=2{[(√5-1)/2+1/4]²-1/16}-1
=2{[(2√5-2+1)/4]²-1/16}-1
=2[(2√5-1)²/16-1/16]-1
=(20-4√5+1-1)/8-1
=5/2-√5/2-1
=(3-√5)/2