已知x=根号2-1,求x²+3x-1的值

已知x=根号2-1,求x²+3x-1的值
已知x=根号2-1,求x²+3x-1的值

已知x=根号2-1,求x²+3x-1的值
x²+3x-1
=(√2-1)²+3(√2-1)-1
=3-2√2+3√2-3-1
=√2-1

x²+3x-1
=x²+2x+x+1-1-1
=x²+2x+1+x-2
=(x+1)²+x-2
=(√2-1+1)²+√2-1-2
=(√2)²+√2-3
=2+√2-3
=√2-1