求几道数学题答案现在就要12分悬赏计算(1) (5a+4c+7b)+(5c-3b-6a)(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)(3) (2x^2-1\2+3x)-4(x-x^2+1\2)(4) 3x^2-{7x-(4x-3)-2x^2}先化简下式,再求值(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2

求几道数学题答案现在就要12分悬赏计算(1) (5a+4c+7b)+(5c-3b-6a)(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)(3) (2x^2-1\2+3x)-4(x-x^2+1\2)(4) 3x^2-{7x-(4x-3)-2x^2}先化简下式,再求值(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2
求几道数学题答案现在就要12分悬赏
计算
(1) (5a+4c+7b)+(5c-3b-6a)
(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)
(3) (2x^2-1\2+3x)-4(x-x^2+1\2)
(4) 3x^2-{7x-(4x-3)-2x^2}
先化简下式,再求值
(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2

求几道数学题答案现在就要12分悬赏计算(1) (5a+4c+7b)+(5c-3b-6a)(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)(3) (2x^2-1\2+3x)-4(x-x^2+1\2)(4) 3x^2-{7x-(4x-3)-2x^2}先化简下式,再求值(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2
(5a+4c+7b)+(5c-3b-6a)
=5a+4c+7b+5c-3b-6a
=(5a-6a)+(7b-3b)+(4c+5c)
=-a+4b+9c
(8xy-x^2+y^2)-（x^2-y^2+8xy）
=8xy-x^2+y^2-x^2+y^2-8xy
=-2x^2+2y^2
2x^2-1\2+3x)-4(x-x^2+1\2)
=2x^2+4x^2+3x-4x-1/2-2
=6x^2-x-5/2
3x^2-[7x-(4x-3)-2x^2]
=3x^2-[7x-4x+3-2x^2]
=3x^2-3x-3+2x^2
=5x^2-3x-3
(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2
=-x^2+2x^2+4x+5x+5-4
=x^2+9x+1
x=-2
当X=-2
x^2+1+9x=(-2)^2+1+9*(-2)
=4+1-18
=-13

(1) (5a+4c+7b)+(5c-3b-6a)
=5a-6a+4c+5c+7b-3b
=-a+9c+4b
(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)
=8xy-8xy-x^2-x^2+y^2+y^2
=-2x^2+2y^2
(3) (2x^2-1\2+3x)-4(x-x^2+1\2)
=2x^2+4x^2+3x-4x-...

全部展开

(1) (5a+4c+7b)+(5c-3b-6a)
=5a-6a+4c+5c+7b-3b
=-a+9c+4b
(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)
=8xy-8xy-x^2-x^2+y^2+y^2
=-2x^2+2y^2
(3) (2x^2-1\2+3x)-4(x-x^2+1\2)
=2x^2+4x^2+3x-4x-1/2-2
=6x^2-x-5/2
(4) 3x^2-{7x-(4x-3)-2x^2}
=3x^2-(7x-4x+3-2x^2)
=3x^2+2x^2-3x-3
=5x^2-3x-3
先化简下式，再求值
(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2
=-x^2+2x^2+4x+5x+5-4
=x^2+9x+1
x=-2
所以
原式=4-18+1=-13

收起

1) (5a+4c+7b)+(5c-3b-6a)
=5a+4c+7b+5c-3b-6a
=-a+4b+9c
(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)
=8xy-x^2+y^2-x^2+y^2-8xy
=-2x^2+2y^2
=2(y^2-x^2)
(3) (2x^2-1\2+3x)-4(x-x^...

全部展开

1) (5a+4c+7b)+(5c-3b-6a)
=5a+4c+7b+5c-3b-6a
=-a+4b+9c
(2) (8xy-x^2+y^2)-(x^2-y^2+8xy)
=8xy-x^2+y^2-x^2+y^2-8xy
=-2x^2+2y^2
=2(y^2-x^2)
(3) (2x^2-1\2+3x)-4(x-x^2+1\2)
=2x^2-1/2+3x-4x+4x^2-2
=6x^2-x-5/2
4) 3x^2-{7x-(4x-3)-2x^2}
=3x^2-{7x-4x+3-2x^2}
=3x^2-7x+4x-3+2x^2
=5x^2-3x-3
(-x^2+5+4x)+(5x-4+2x^2) 其中x=-2
=-x^2+5+4x+5x-4+2x^2
=x^2+9x+1
将x=2带入上式：
（-2）^2+9*(-2)+1
=-13

收起

1)5a+4c+7b+5c-3b-6a=-a+4b+9c
2)8xy-x^2+y^2-x^2+y^2-8xy=2(y^2-x^2)
3)2x^2-1/2+3x-4x+4x^2-2=6x^2-x-5/2=47/2
4)3x^2-（7x-4x+3-2x^2)
=3x^2-3x-3+2x^2=5x^2-3x-3=23
5)-x^2+5+4x+5x-4+2x^2=x^2+9x+1=-13

这些都是把括号拆开就行。 1,原式＝5a+4c+7b+5c-3b-6a=9c+4b-a 2原式＝y-4x 3原式＝6x^2-x-1 4原式＝5x^2-x-1 分解应式 原式＝x^+9x+1最后答案-13