19、单选 lim _-|||-A 1-|||-B) dfrac (4)(9)-|||-C dfrac (2)(3)-|||-D dfrac (9)(4)

lim _(xarrow 4)dfrac (sqrt {1+2x)-3}(x-4)= (-|||-A dfrac (2)(3) .-|||-B 2-|||-C

(B) dfrac (9)(4pi {varepsilon )_(0)a}-|||-(C) -dfrac (9)(8pi {varepsilon )_(0)a}

10、单选-|||-极限 lim _-|||-A-|||-dfrac (1)(6)-|||-B dfrac (1)(2)-|||-C -dfrac (1)(3)

极限 lim _-|||-A-|||-dfrac (5)(3)-|||-B dfrac (7)(3)-|||-C) 1-|||-D 3

-dfrac (2)(3) C. dfrac (2)(3) D. dfrac (1)(9)

(4) lim _(xarrow 1)(dfrac (1)(1-x)-dfrac (3)(1-{x)^3});

B. dfrac {1)(2) . C. dfrac (2)(3) . D. dfrac (3)(4)

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

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

lim _(xarrow 1)(dfrac (a)(1-{x)^2}+dfrac (x)(x-1))=dfrac (3)(2) = __