(B) _(x)(dfrac (y-b)(a)).-|||-(C) dfrac (1)(|a|)(f)_(x)(y-b). (D) dfrac (1)(|a|)(f)_(x)(dfrac (y-b)(a))

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

3、设 (x,y)=arctan dfrac (x)(y), 则 (1,1)=-|||-(A)1; (B)0; (C) dfrac {1)(2),dfrac

(B) X=Y =dfrac (1)(2),-|||-(C) X=Y =dfrac (1)(4), (D) X=Y =0.A、AB、BC、CD、DA、AB

设 =dfrac (y)(f({x)^2-(y)^2)} ,其中f(u)为可导函数,验证-|||-.dfrac (1)(x)dfrac (dz)(partial

3.设 =dfrac (y)(f({x)^2-(y)^2)} ,其中f为可微函数,验证-|||-dfrac (1)(x)dfrac (partial z)(pa

7.设 =dfrac (y)(f({x)^2-(y)^2)} 其中f为可导函数,验证: dfrac (1)(x)dfrac (partial z)(partia

(4)已知 =xln x, 则 y(10) 等于 ()-|||-(A) -dfrac (1)({x)^9} (B) dfrac (1)({x)^9} (C) d

(B) dfrac (1)(2)(X)^2+dfrac (1)(2)(Y)^2 服从x^2分布.-|||-(C) dfrac (1)(3)((X+Y))^2 服

(5)设 (x,y)=ln (x+dfrac (y)(2x)) ,则 _(y)(1,0)= () .-|||-(A)1 (B) dfrac (1)(2) (C)

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