Question

完全平方公式(写过程~）（1) (x+y+1）^2(2) (x-y+z)^2(3) (m+n-2)^2

Answer 1

(x+y+1）^2

=[(x+y)+1]^2

=(x+y)^2+2(x+y)+1

=x^2+2xy+y^2+2x+2y+1

(x-y+z)^2

=[(x-y)+z]^2

=(x-y)^2+2(x-y)z+z^2

=x^2-2xy+y^2+2xz-2yz+z^2

(m+n-2)^2

=[(m-n)-2]^2

=(m-n)^2-4(m-n)+4

=m^2-2mn+n^2-4m+4n+4