5*（a+b)-a-b=5a+5b-a-b+4a+4b
X^2+3X-10=(x+5)(X-2)
(m+n)^2(m-n)^2=(m^2+2mn+n^2)(m^2-2mn+n^2)=(M^4-2m^3n+m^2n^2+2m^3n-4m^2n^2+2mn^3+m^2n^2-2mn^3+n^4)=m^4-2m^2n^2+n^4=(m^2-n^2)^2
PS:M^2是m的平方,m^4是m的四次方