{3x-y=6   t+y=6}

已知｛x=3t^4+6t,y=t^3-3t｝ 求导数 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 已知{x=3t^2+1,y=t^6+2t^3},求导数 已知x,y,z,t,满足方程组x+y+z=6,2x-z+t=-2,y+z+t=4,x-2y+t=-4,求想,x,y,z, 已知xy=-2,x-y=3,求（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y