整式计算(1)3a[(b^2)-3a(b-3a)]+b[(9a^2)-3ab+(b^2)](2)[(4x-1/2·y)(x^2-2xy)因式分解(1)ab-a+b-1(2)(a+b+c)^2-(a-b-c)^2
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整式计算(1)3a[(b^2)-3a(b-3a)]+b[(9a^2)-3ab+(b^2)](2)[(4x-1/2·y)(x^2-2xy)因式分解(1)ab-a+b-1(2)(a+b+c)^2-(a-b-c)^2
整式计算
(1)3a[(b^2)-3a(b-3a)]+b[(9a^2)-3ab+(b^2)]
(2)[(4x-1/2·y)(x^2-2xy)
因式分解
(1)ab-a+b-1
(2)(a+b+c)^2-(a-b-c)^2
整式计算(1)3a[(b^2)-3a(b-3a)]+b[(9a^2)-3ab+(b^2)](2)[(4x-1/2·y)(x^2-2xy)因式分解(1)ab-a+b-1(2)(a+b+c)^2-(a-b-c)^2
整式计算
(1) 3a[b²-3a(b-3a)]+b(9a²-3ab+b²)
=3a(b²-3ab+9a²)+9a²b-3ab²+b³
=3ab²-9a²b+27a³+9a²b-3ab²+b³
=27a³+b³
(2)(4x-½y)(x²-2xy)
=4x³-8x²y-½x²y+xy²
=4x³-17/2x²y+xy²
此两题没什么技巧.展开就行.主要是要认真!
注意写的时候字母按顺序写(比如a在前b在后,x在前y在后,这样就不容易出错)
因式分解
(1) ab-a+b-1
=a(b-1)+(b-1)
=(b-1)(a+1)
(提a,再提b-1)
(2)(a+b+c)²-(a-b-c)²
=(a+b+c+a-b-c)[(a+b+c)-(a-b-c)]
=2a x 2(b+c)
=4a(b+c)
参考资料
a²-b²=(a+b)(a-b)
（1）式=3ab^2-9a^2b+27a^3+9ba^2-3ab^2+b^3
=27a^3+b^3
(2) 式=4x^3-8x^2y-yx^2/2+xy^2
=4x^3-17yx^2/2+xy^2
(1)式=a(b-1)+b-1
=(b-1)(a+1)
(2)式=（a+b+c+a-b-c）(a+b+c-a+b+c)
=2a(2b+2c)
=4a(b+c)
因式分解（1）a (a - b) b (b - a) = a (a - b) - b (a - b) = (a - b)(a - b ) = (a - b)(a b)(a - b)