
利用因式分解计算
展开全部
(2)80X3.5²+160X3.5X1.5+80X1.5²
=80X(3.5²+2X3.5X1.5+1.5²)
=80X(3.5+1.5)²
=80X25
=20X4X25
=2000
(3)804x796
=(800+4)(800-4)
=800²-4²
=640000-16
=639984
=80X(3.5²+2X3.5X1.5+1.5²)
=80X(3.5+1.5)²
=80X25
=20X4X25
=2000
(3)804x796
=(800+4)(800-4)
=800²-4²
=640000-16
=639984
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