计算:-|||-(1) dfrac (ny)(mx)cdot dfrac (my)(nx)-|||-;(2) dfrac (12x)(7y)div 8(x)^2y-|||-;(3) dfrac ({x)^2-2x+1}({x)^2-1}div dfrac (x-1)({x)^2+x}-|||-;(4) ((-dfrac {3b)(2a))}^2计算：(1) 计算:-|||-(1) dfrac (ny)(mx)cdot dfrac (my)(nx)-|||-;(2) dfrac (12x)(7y)div 8(x)^2y-|||-;(3) dfrac ({x)^2-2x+1}({x)^2-1}div dfrac (x-1)({x)^2+x}-|||-;(4) ((-dfrac {3b)(2a))}^2 (3 计算:-|||-(1) dfrac (ny)(mx)cdot dfrac (my)(nx)-|||-;(2) dfrac (12x)(7y)div 8(x)^2y-|||-;(3) dfrac ({x)^2-2x+1}({x)^2-1}div dfrac (x-1)({x)^2+x}-|||-;(4) ((-dfrac {3b)(2a))}^2 4 计算:-|||-(1) dfrac (ny)(mx)cdot dfrac (my)(nx)-|||-;(2) dfrac (12x)(7y)div 8(x)^2y-|||-;(3) dfrac ({x)^2-2x+1}({x)^2-1}div dfrac (x-1)({x)^2+x}-|||-;(4) ((-dfrac {3b)(2a))}^2

直线dfrac (x-1)(1)=dfrac (y)(2)=dfrac (z+3)(-2)-|||-__ __-|||-__与平面dfrac (x-1)(1)=

求椭球面dfrac ({x)^2}(2)+dfrac ({y)^2}(3)+dfrac ({z)^2}(4)=1上点dfrac ({x)^2}(2)+dfrac

下列选项中曲面dfrac ({x)^2}(4)+dfrac ({y)^2}(1)+dfrac ({z)^2}(9)=3上点dfrac ({x)^2}(4)+df

直线dfrac (x-1)(2)=dfrac (y)(-1)=dfrac (z-2)(3)-|||-__与直线dfrac (x-1)(2)=dfrac (y)(

(B) dfrac (x)(y)((y+1))^2-|||-(C) ^2((x+dfrac {1)(x))}^2. (D) dfrac (y)(x)((y+1)

设L为椭圆dfrac ({x)^2}(2)+dfrac ({y)^2}(3)=1，其周长为a，则dfrac ({x)^2}(2)+dfrac ({y)^2}(3

(7) dfrac (dy)(dx)=dfrac (2{x)^3+3x(y)^2+x}(3{x)^2y+2(y)^3-y}

下列直线中,经过点 A ( -1 , 2 ) 的是 ( ).A.y=2x-1B.y=-dfrac (1)(3)x+dfrac (7)(3)C.y-3=-d

2.已知 dfrac (x)(x+y)=dfrac (1)(3) ,求 dfrac ({x)^2-(y)^2}(2xy+{y)^2} 的值.

dfrac (1)(5)(X)_(1)+dfrac (2)(5)(X)_(2)+dfrac (2)(5)(X)_(3)-|||-D .dfrac (1)(7)(