x Y-8x-4y 11-搜答案-搜狗做题网

x=3/2,y=-2/3xy=3/2*(-2/3)=-12xy-1/2（4xy-8x²y²）+2（3xy-5x²y²）=2xy-2xy+4x²y

题目写错应该是求（6xy+7y)+[8x-(5xy-y+6x)]（6xy+7y)+[8x-(5xy-y+6x)]=6xy+7y+8x-5xy+y-6x=xy+2x+8y=xy+2(x+4y)=5+2×

（5X-4Y-3XY）-（8X-Y+2XY）=-(3X+3Y)-5XY=-3*6+4*5=2

xy^2-4x 因式分解

xy^2-4x=x(y+2)(y-2)-2a^2+4ab-2b^2=-(a-b)^2a^2(x-y)+b^2(y-x)=(x-y)(a+b)(a-b)(a^2+b^2)^2-4a^2b^2=(a+b)

(-3x^y+2xy)-(4x^+xy)=-3x^y+2xy-4x^-xy=-3x^y+xy-4x^所以填上-3x^y+xy-4x^

（x^2+3x+2)(3+8x+4x^2)-90=（x+2）（x+1）（2x+1）（2x+3）-90=（x+2）（2x+1）（x+1）（2x+3）-90=（2x^2+5x+2）(2x^2+5x+3)-

-4x²y-8xy²+2x²y-3xy²=-2x²y-11xy²=-xy(2x+11y)

1、已知2x²+xy=10,3y²+2xy=6,求4x²+8xy+9y²的值为?分析：通过观察,可以把8xy拆成2xy+6xy,分别于剩余的两项组合,并提取公因

-3(2x²-xy)+4(x²+xy-6)

-3(2x²-xy)+4(x²+xy-6)=6x²+3xy+4x²+4xy-24=-2x²+7xy-24

3x²+2x²-3x-(-x+5x²)=3x²+2x²-3x+x-5x²=-2x其中x=314时,-2x=-2*314=-6285xy-8x

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解3x²y+6xy-4x-8=(3x²y-4x)+(6xy-8)=x(3xy-4)+2(3xy-4)=(x+2)(3xy-4)

% matlab 程序X=[7 4 8.5 9.5 3 1 8 5];Y=[11 8.5

-3(2x^2-xy)+4(x^2+xy-6)

-3(2x^2-xy)+4(x^2+xy-6)=-6x^2+3xy+4x^2+4xy-24=-2x^2+7xy-24再问：thankyou~

x²+4y²≥2√(x²*4y²)=4xy所以x²+4y²+4xy≥4xy+4xy=8xy

(5xy+4x+7y)+(6x-3xy)-(4xy-3y)=5xy+4x+7y+6x-3xy-4xy+3y=(5xy-3xy-4xy)+(4x+6x)+(7y+3y)=-2xy+10x+10y=-2x

4x²+7xy-y²=04(x/y)²+7(x/y)-1=0∴x/y=(-7±√65)/8

原式=3x(x-2y)-4(x-2y)=(x-2y)(3x-4)

(5.2x²y-3.4xy+8x³)+2(2.2xy-4x³-2.3x²y)=5.2x²y-3.4xy+8x³+4.4xy-8x³

由xy+x=16,得x=16/(y+1)代入xy-x=8,得16y/(y+1)-16/(y+1)=8=>16(y-1)/(y+1)=8=>(y-1)/(y+1)=1/2移项,通分得y-3/2(y+1)