Question

已知y²=3.14,（x-z）²=0.14,则（x+y-z）（x-y-z）=

Answer 1

已知y²=3.14,（x-z）²=0.14,

则,y^2-(x-z)^2=3.14-0.14=3

[y+(x-z)][y-(x-z)]=3

(y+x-z)(y-x+z)=3

-（x+y-z)(x-y-z)=3

所以,（x+y-z）（x-y-z）=-3

若（a-b-1）（a-b-3）=5

则,（a-b)^2-4(a-b)+3=5

(a-b)^2-4(a-b)=2

那么,（a-b-2）²

=[(a-b)-2]^2

=（a-b)^2-4(a-b)+4

=2+4

=6