{3x+5x=19 3x-5y=-1

用递归法求y=x-(x*x*x/3!)+(x*x*x*x*x/5!)-(x*x*x*x*x*x*x/7!)+. 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) y=(x-1)(x-2)(x-3)(x-4)(x-5)(x-6)(x-7)(x-8)(x-9)(x-10)的导数在x=1 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( （2x+y-1)(2x-y+1)-(3x+y)(3x-y),其中x=5分之1, 设变量xy满足 x+y-3 x-y+1 3x-y+5 z=x+y/x 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 求函数y=\x-1\+\x-2\+\x-3\+\x-4\+\x-5\+\x-6\+.+\x-10\的最小值 x=3,y=-x+5(x＞1) y=-x+5(x≤1),y=? （5x+3y)(3y-5x)-(4x-y)(4y+x)=