若a=根号2-1,则a²-根号2a的值是

若a=根号2-1,则a²-根号2a的值是
若a=根号2-1,则a²-根号2a的值是

若a=根号2-1,则a²-根号2a的值是
解
a=√2-1
a²-√2a
=a(a-√2)
=(√2-1)(√2-1-√2)
=(√2-1)×(-1)
=1-√2

a²-根号2a
=a(a-根号2)
=(根号2-1)×[(根号2-1)-根号2]
=(根号2-1)×(-1)
=2-根号2