(1)
9(m+n)²-16(m-n)²
=[3(m+n)+4(m-n)][3(m+n)-4(m-n)]
=(7m-n)(-m+7n)
(2)
(x+y)²+10(x+y)+25
=(x+y+5)²
(3)
4a²b²-(a²+b²)²
=(2ab)²-(a²+b²)²
=(2ab+a²+b²)(2ab-a²-b²)
=-(a+b)²(a-b)²
(4)
(c²-a²-b²)²-4a²b²
=(c²-a²-b²)²-(2ab)²
=(c²-a²-b²+2ab)(c²-a²-b²-2ab)
=[c²-(a-b)²][c²-(a+b)²]
=(c+a-b)(c-a+b)(c+a+b)(c-a-b)
(5)
(x+p)²-(x-q)²
=(x+p+x-q)(x+p-x+q)
=(p+q)(2x+p-q)
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