Đáp án:
a, Ta có :
$|9+x| = 2x
<=> \(\left[ \begin{array}{l}9+x=2x\\9+x = -2x\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=9\\x=-3\end{array} \right.\)
b, Ta có :
$|5x| - 3x = 2$
$ <=> |5x| = 3x + 2$
<=> \(\left[ \begin{array}{l}5x=3x+2\\5x=-3x-2\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=1\\x=-1/4\end{array} \right.\)
c, $|x+6| - 9 = 2x$
$=> |x+6| = 2x + 9$
<=>\(\left[ \begin{array}{l}x+6=2x+9\\x+6=-2x-9\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=-3\\x=-5\end{array} \right.\)
d, $|2x-3| = x + 21$
<=> \(\left[ \begin{array}{l}2x-3=x+21\\2x-3=-x-21\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=24\\x=-6\end{array} \right.\)
Tổng Quát
$A(x) = B(x)$
<=> \(\left[ \begin{array}{l}A(x) = B(x)\\A(x) = -B(x)\end{array} \right.\)
Giải thích các bước giải:
