若f（x）=x²-根号2,则f【f（根号2）】等于?

若f（x）=x²-根号2,则f【f（根号2）】等于?
若f（x）=x²-根号2,则f【f（根号2）】等于?

若f（x）=x²-根号2,则f【f（根号2）】等于?
∵f(x)=x²-√2
∴f﹙√2﹚=﹙√2﹚²-√2
=2-√2
则f[f(√2)=f(2-√2)
=(2-√2)²-√2
=4-4√2 +2-√2
=6-5√2

f(√2)=（√2）²-√2 =2-√2
则f[f(根号2)]=f(2-√2)=(2-√2)²-√2=4-4√2 +2-√2=6-5√2

6-5根号2是对的

f(x)=x²-√2
f(√2)=(√2)²-√2
=2-√2
f(f(√2))=(2-√2)²-√2
=4+2-4√2-√2
=6-5√2