1/x+1/y=1/12 (5+9)/x+9/y=1 这个方程怎样解

计算：1.y/4x²-1/12y²+1/6xy 2.3/x-6/1-x-x+5/x²-x3.x/x-y×y²/x+y-x四次方y/x四次方-y四次方÷x²/x²+y²解方程：1.x-1/（x-2）+1=1/2-x2.x+1/x-1-4/x²-1=13.1/x+3-2/3-x=1/x²-9 解方程组 2x-y=5 2y/x-x/y=12x-y=52y/x-x/y=1 x.y都是自然数,且x(x-u)-y(y-x)+12,求x.y得值快1且x(x-y)-y(y-x)=12 {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 (x+y)/6+(x-y)/10=1,(x+y)/6-(x-y)/10=5 4x³y+12x²y²+9x y³/4x³-9x y²,其中x=1,y=1. (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) (x-y)/4+(x+y)/5=1/4 (x+y)/9-(x-y)/3=//2(x-y)/4+(x+y)/5=1/4(x+y)/9-(x-y)/3=//2 ｛x-y=4 ｛5x-y=110 4x-y=－1 9y-x=110 解方程组 3(x+y)-2(x-y)=9,5(x+y)+2(x-y)=-1 解方程组:{3(x+y)-2(x-y)=9,5(x+y)+2(x-y)=-1} 4(x+2)=1-5y 4(x+y)-3(x-y)=12 先化简再求值 x(9x-y)-y(y-x)+(x-y)的平方,其中x=-1,y=2 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 导数的计算练习题导数的计算（1）y=x^5 （2)y=sinx(3)y=1/x^3(4)y=5^√x(5)y=cosx(6)y=5^x(7)y=log3^x(8)y=lnx(9)f(x)=x^3-x^2-x+1(10)y=2x^3-3x^2+4x-1(11)y=x inx（12）y=xsinx-cosx(13)y=cosx/x(14)y=3x(x^2+2)(15)f(x)=(x-1)^2+3(x-1)(16)f(x)=1 3x-y+x=3 4【X-y-1】=3【1-y】-1 5x-4y+4x=3 2x+y-3x=11 【 x除以2 】-【y 除以3】 =2 2x+7y-3x=19 x+y+x=12 3x+2y-x=18 分式的加减:[(x/y-y/x)除以（x+y）+x（1/y-1/x)]除以1+x/y,其中x=5,y=2 [(y*y*y-y)/(xy+1)*(xy+1)-(x+y)*(x+y)]/[(x+y)*y/(x+1)]其中x=-11,y=1/12,化简再求值.