A=4ab-2b²-a²,B=3b²-2a²+5ab当a=1.5 b=-2分之1 求3B-4A2.计算.(1)8x-(5x-4)(2)(3x-2y)-(-x-y)(3)2(x-3)-3(2x-5)(4)5(-m+n)-7(m-n)(5)-3(a+b+c)
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![A=4ab-2b²-a²,B=3b²-2a²+5ab当a=1.5 b=-2分之1 求3B-4A2.计算.(1)8x-(5x-4)(2)(3x-2y)-(-x-y)(3)2(x-3)-3(2x-5)(4)5(-m+n)-7(m-n)(5)-3(a+b+c)](/uploads/image/z/1995167-47-7.jpg?t=A%EF%BC%9D4ab%EF%BC%8D2b%26%23178%3B%EF%BC%8Da%26%23178%3B%2CB%EF%BC%9D3b%26%23178%3B%EF%BC%8D2a%26%23178%3B%EF%BC%8B5ab%E5%BD%93a%EF%BC%9D1.5+b%EF%BC%9D%EF%BC%8D2%E5%88%86%E4%B9%8B1+%E6%B1%823B%EF%BC%8D4A2.%E8%AE%A1%E7%AE%97.%EF%BC%881%EF%BC%898x%EF%BC%8D%EF%BC%885x%EF%BC%8D4%29%EF%BC%882%EF%BC%89%EF%BC%883x%EF%BC%8D2y%29%EF%BC%8D%EF%BC%88%EF%BC%8Dx%EF%BC%8Dy%29%EF%BC%883%EF%BC%892%EF%BC%88x%EF%BC%8D3%EF%BC%89%EF%BC%8D3%EF%BC%882x%EF%BC%8D5%EF%BC%89%EF%BC%884%EF%BC%895%EF%BC%88%EF%BC%8Dm%EF%BC%8Bn%29%EF%BC%8D7%EF%BC%88m%EF%BC%8Dn%29%285%EF%BC%89%EF%BC%8D3%EF%BC%88a%EF%BC%8Bb%EF%BC%8Bc%29)
A=4ab-2b²-a²,B=3b²-2a²+5ab当a=1.5 b=-2分之1 求3B-4A2.计算.(1)8x-(5x-4)(2)(3x-2y)-(-x-y)(3)2(x-3)-3(2x-5)(4)5(-m+n)-7(m-n)(5)-3(a+b+c)
A=4ab-2b²-a²,B=3b²-2a²+5ab
当a=1.5 b=-2分之1 求3B-4A
2.计算.
(1)8x-(5x-4)
(2)(3x-2y)-(-x-y)
(3)2(x-3)-3(2x-5)
(4)5(-m+n)-7(m-n)
(5)-3(a+b+c)-4(-a-5b+6c)
去括号的知识
A=4ab-2b²-a²,B=3b²-2a²+5ab当a=1.5 b=-2分之1 求3B-4A2.计算.(1)8x-(5x-4)(2)(3x-2y)-(-x-y)(3)2(x-3)-3(2x-5)(4)5(-m+n)-7(m-n)(5)-3(a+b+c)
A=4ab-2b²-a²,B=3b²-2a²+5ab
当a=1.5 b=-2分之1 求3B-4A
3B-4A
=3(3b²-2a²+5ab) - 4(4ab-2b²-a²)
=9b²-6a²+15ab-16ab+8b²+4a²
=17b²-2a²-ab
=17/4-18/4+3/4
= 1/2
2.计算.
(1)8x-(5x-4) = 8x-5x+4=3x+4
(2)(3x-2y)-(-x-y) = 3x-2y+x+y = 4x-y
(3)2(x-3)-3(2x-5)= 2x-6-6x+15=-4x+9
(4)5(-m+n)-7(m-n) = -5m+5n-7m+7n=-12m+12n
(5)-3(a+b+c)-4(-a-5b+6c) = -3a-3b-3c+4a+20b-24c = a+17b-27c
3B=3 ×(3b²-2a²+5ab)= 9b² - 6a²+15ab
4A=4 × (4ab-2b²-a²) =16ab - 8b² - 4a² = - 8b² - 4a²+16ab
所以3B-4A=17b²-2a²-ab=17/4-18/4+...
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3B=3 ×(3b²-2a²+5ab)= 9b² - 6a²+15ab
4A=4 × (4ab-2b²-a²) =16ab - 8b² - 4a² = - 8b² - 4a²+16ab
所以3B-4A=17b²-2a²-ab=17/4-18/4+3/4= 1/2
(1)原式=8x-5x+4=3x+4
(2)原式=3x-2y+x+y=4x-y
(3)原式=2x-6-6x+15= -4x+9
(4)原式=-5m+5n-7m+7n= -12m+12n
(5)原式=-3a-3b-3c+4a+20b-24c=a+17b-27c
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