a) $\sqrt{49x - 98} - 24\sqrt{\dfrac{x - 2}{64}} - \sqrt{9x - 18} = 7 (ĐKXĐ: x \geq 2)$
$⇔ \sqrt{49(x -2)} - 24\dfrac{1}{8} . \sqrt{x - 2} - \sqrt{9(x -2)} = 7$
$⇔ 7\sqrt{x - 2} - 3\sqrt{x - 2} - 3\sqrt{x - 2} = 7$
$⇔ \sqrt{x - 2} = 7$
$⇒ x - 2 = 49$
$⇔ x = 51 (T/m)$
b) $\sqrt{4x^2 - 20x + 25} = 3 (ĐKXĐ: ∀ x ∈ R)$
$⇔ \sqrt{(2x - 5)^2} = 3$
$⇔ |2x - 5| = 3$
⇔\(\left[ \begin{array}{l}2x - 5 = 3\\2x - 5 = -3\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x = 4 (T/m)\\x =1 (T/m) \end{array} \right.\)
