（1）已知a^2+2ab+b^2=0,
(a+b)^2=0,a+b=0,
代數(shù)式a(a+4b)-(a+2b)(a-2b)
=a^2+4ab-a^2+4b^2
=4b(a+b)
=0
（2）因式分解；m^2(p-q)-p+q
=m^2(p-q)-(p-q)
=(p-q)(m^2-1)
=(p-q)(m+1)(m-1).