已知x=1/根号2-1,求x²-2x-1的值
问题描述:
已知x=1/根号2-1,求x²-2x-1的值
答
x=1/根号2-1
=(√2+1)/[(√2+1)(√2-1)]
=√2+1
x²-2x-1
=x²-2x+1-2
=(x-1)²-2
=(√2+1-1)²-2
=2-2
=0