Đáp án: x=424
Giải thích các bước giải:
$\begin{array}{l}
\frac{{392 - x}}{{32}} + \frac{{390 - x}}{{34}} + \frac{{388 - x}}{{36}} + \frac{{386 - x}}{{38}} + \frac{{384 - x}}{{40}} = - 5\\
\Rightarrow \frac{{392 - x}}{{32}} + \frac{{390 - x}}{{34}} + \frac{{388 - x}}{{36}} + \frac{{386 - x}}{{38}} + \frac{{384 - x}}{{40}} + 5 = 0\\
\Rightarrow \frac{{392 - x}}{{32}} + 1 + \frac{{390 - x}}{{34}} + 1 + \frac{{388 - x}}{{36}} + 1 + \frac{{386 - x}}{{38}} + 1 + \frac{{384 - x}}{{40}} + 1 = 0\\
\Rightarrow \frac{{392 - x + 32}}{{32}} + \frac{{390 - x + 34}}{{34}} + \frac{{388 - x + 36}}{{36}} + \frac{{386 - x + 38}}{{38}} + \frac{{384 - x + 40}}{{40}} = 0\\
\Rightarrow \frac{{424 - x}}{{32}} + \frac{{424 - x}}{{34}} + \frac{{424 - x}}{{36}} + \frac{{424 - x}}{{38}} + \frac{{424 - x}}{{40}} = 0\\
\Rightarrow \left( {424 - x} \right)\left( {\frac{1}{{32}} + \frac{1}{{34}} + \frac{1}{{36}} + \frac{1}{{38}} + \frac{1}{{40}}} \right) = 0\\
\Rightarrow 424 - x = 0\\
\Rightarrow x = 424
\end{array}$
