Đáp án:
$C = 25$
Giải thích các bước giải:
$\quad C =\lim\limits_{x\to 0}\dfrac{(1+3x)^3 - (1-4x)^4}{x}$
$\to C = \lim\limits_{x\to 0}\dfrac{(1+3x)^3 - 1 + 1 -(1-4x)^4}{x}$
$\to C = \lim\limits_{x\to 0}\dfrac{3x[(1+3x)^2 + 2 + 3x] + [1- (1-4x)^2][1+(1-4x)^2]}{x}$
$\to C = \lim\limits_{x\to 0}\dfrac{3x[(1+3x)^2 + 2 + 3x] + 4x(2-4x)[1+(1-4x)^2]}{x}$
$\to C = \lim\limits_{x\to 0}\left\{3[(1+3x)^2 + 2 + 3x] + 8(1-2x)[1+(1-4x)^2]\right\}$
$\to C = 3[(1+3.0)^2 + 2 + 3.0] + 8(1-2.0)[1+(1-4.0)^2]$
$\to C = 25$
