Bài 1:
$a) (\dfrac{6}{5})^{x} = \dfrac{216}{125}$
$⇒ (\dfrac{6}{5})^{x} = (\dfrac{6}{5})³$
$⇒ x = 3$
$Vậy$ $x = 3$
$b) 17 - |\dfrac{2}{3} -4x| = 9$
$⇒ |\dfrac{2}{3} -4x| = 8$
$⇒ \left[ \begin{array}{l}\dfrac{2}{3} -4x=8\\\dfrac{2}{3} -4x=-8\end{array} \right. ⇒ \left[ \begin{array}{l}x=\dfrac{-11}{6}\\x=\dfrac{13}{6}\end{array} \right.$
$Vậy$ $x ∈$ {$\dfrac{-11}{6}; \dfrac{13}{6}$}
Bài 2:
$\text {Đặt $\dfrac{x}{3}$ = $\dfrac{y}{4}$ = $\dfrac{z}{7}$ = m }$
$\text {⇒ x = 3m; y = 4m; z = 7m}$
$\text {Mà x.y = 48 }$
$⇒ 3m.4m = 48$
$⇒ 12m² = 48$
$⇒ m² = 4$
$⇒ m = ±2$
$\text {TH1: x = 3.2 = 6; y = 4.2 = 8; z = 7.2 = 14}$
$\text {TH2: x = 3.(-2) = -6; y = 4.(-2) = -8; z = 7.(-2) = -14}$
