(1)a³b³+a²b²-ab=ab[(ab)²+ab-1]
=ab[(ab+½)²-3/4].
(2)﹣8a³y+12a²y²-16ay³=﹣16a²y(y²-3y/4+a/2)
=﹣16a²y[(y-3/2)²+a/2-9/4].
(3)﹣3a³-6a²m+12m=﹣3a(a²+2am)+12m
=﹣3a[(a+m)²-m²]+12m
=﹣3a(a+m)²+3am²+12m
=﹣3a(a+m)²+3a[(m+2/a)²-4/a²]
=﹣3a(a+m)²+3a(m+2/a)²-12/a.
(所给式子的因式分解,通常用于求式子的最大值与最小值,具体根据题目要求)
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