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3x 2y 5 y 2x 1

(1)3x-2y+1+3y-2x-5中3x和-2x,-2y和3y,1和-5是同类项,3x-2y+1+3y-2x-5=(3-2)x+(-2+3)y+(1-5)=x+y-4.(2)3x 2 y-2xy 2 + 1 3 xy 2 - 3 2 yx 2 中3x 2 y和- 3 2 yx 2 ,-2xy 2 和 1 3 xy 2 是同类项,3x 2 y-2xy 2 + 1 3 xy 2 - 3 2...

3x+2y=5 (1) y=2x-1 (2) 将(2)代入(1) 3x+2(2x-1)=5 3x+4x-2=5 7x=7 x=1 y=1

一3x²y+2X²y+3xy²一2xy² =-x²y+xy² =-1²x5+1x5² =-5+25 =20

(3x-2y)(y-3x)-(2x-y)(3x+y) =9xy-2y²-9x²-6x²+xy+y² =-15x²-y²+10xy 把x=1/5 y=1代入 原式 =-15x²-y²+10xy =-3/5-1+2 =2/5

把第一个公式带入第二个公式里就得到 2(2x-1)-3x=-5 4x-2-3x=-5 x=-3 再把X=-3带入第一个公式得到 y=2(-3)-1 y=-7

x+y+z=5 ------------------------------------(1) 2x-2y+z=1 ------------------------------------(2) 3x+2y+z=4 -----------------------------------(3) (2)+(3) 得:5x+2z=5 ------------------------(4) (1)*2+(2)得: 4x+3z=11 ---------...

(1)原式=-2x-4x+2y+3x-2y+1=-3x+1,当x=-3时,原式=10;(2)原式=xy-2y2-8xy+6y2-2x2y+30y2-4x2y=-7xy+34y2-6x2y,当x=1,y=-2时,原式=162.

(1)原式=-22x2y4?3x2y÷x3y4=-12x4y5÷x3y4=-12xy(2)原式=4x2-6x+2xy-3y-2xy+2y=4x2-6x-y(3)原式=3(m2+2m+1)-5(m2-1)+2(m2-2m+1)=3m2+6m+3-5m2+5+2m2-4m+2=2m+10(4)原式=-(2x2y-x3y2-12xy3)×2x-1y-1=-2x2y×2x-1y-1+x3y2×2x-1y-1+1...

2x-3y=5m+1 (1) 3x+2y=2-3m (2) 5(1) +(2) 13x-13y = 5(5m+1) +2-3m x-y = (1/13)(22m+7) -1

(1)3x3-1-3x-5+4x-2x3=(3x3-2x3)+(-3x+4x)+(-1-5)=x3+x-6.(2)3x2y3+2xy?7x2y3?32xy+2+4x2y2.=(3x2y3-7x2y3)+(2xy-32xy)+4x2y2+2=-4x2y3+12xy+4x2y2+2.

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