Bài 13 :
a, 5.|$x$|+$(-2)^{4}$ = 56
↔ 5.|$x$|+16 = 56
↔ 5.|$x$| = 56 -16 = 40
↔ |$x$| = 40 : 5 =8
→\(\left[ \begin{array}{l}x=-8\\x=8\end{array} \right.\)
b, 3.|$x$|+$(-3)^{3}$ = 12
↔ 3.|$x$|+ (-27) = 12
↔ 3.|$x$| = 12 - (-27) = 39
↔|$x$| = 39 : 3 = 13
→\(\left[ \begin{array}{l}x=13\\x=-13\end{array} \right.\)
c, |$x$| : 2 + $(-3)^{3}$ = 15 -27
↔|$x$| : 2 + $(-3)^{3}$ = (-12)
↔|$x$| : 2 + $(-27)$ = (-12)
↔|$x$| : 2 = (-12) - (-27) = 15
↔|$x$| = 15 . 2 = 30
→\(\left[ \begin{array}{l}x=30\\x=-30\end{array} \right.\)
d, 25 + 2.|$x$| = $-5^{2}$ +10
↔25 + 2.|$x$| = $(-25)$ +10
↔25 + 2.|$x$| = $(-15)$
↔2.|$x$| = $(-15)$ - 25 = (-40)
↔|$x$| = (-40) : 2 = (-20)
→ $x∈∅$
