4x+8（x+y）=480 4y+9(x+y)=480 = =

解方程组{4x+8(x+y)=480,4y+9(x+y)=480 9y=3x-(x-1),4(x+y)-(2x+4)=8y 4x+8（x+y）=480 4y+9(x+y)=480 = = 已知x²+y²-8x+6y+25=0,求（x-y+4xy/x-y）（x+y-4xy/x+y） 81/8*(-x-y)^6*(x-y)^3*4/9(x+y)^4*(y-x)^2 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) X+Y=9 8X+4Y=56 1.(x^3-x^2-4x+1)/(x^2-3x+2)-(x^3-2x^2-9x+21)/（x^2-5x+6）+（x^2-3x+8）/（x^2-4x+3）2.{(x^2)/（x-y)}*{y/(x+y)}-{(x^4y)/(x^4-y^4)}÷{（x^2/x^2+y^2）^2} y'=（y/x）^2+y/x+4微分方程 [(x+2y)(x-2y)-(x-2y)^2+8y(x+y)]除以4x= 3(x+y）-2（x-y）=11 4（x+y)+3（x-y）=9 ｛（2x+y）2-y（y+4x）-8x｝÷（2x）其中x=-2 【（2x+y）²-y（y+4x）-8x】除以2x,其中x=2 【（2x+y）²-y(y+4x)-8x】÷2x,其中x=100 4x+8(x+y)=840 4y+9(x+y)=840 求x ,y 9x^2+4y^2-12x-8y+8=0