Question

[(m+n)除以2]^2+[(m-n)除以2]^2=(m^2+n^2)除以2.用完全平方计算.

Answer 1

[(m+n)÷2]^2+[(m-n)÷2]^2

=[（m+n)^2+(m-n)^2]/4

=[m^2+2mn+n^2+m^2-2mn+n^2]/4

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

=(m^2+n^2)÷2