Giải câu 5 trang 33 toán VNEN 9 tập 1.
a) Ta có: $\frac{1}{2}$$\sqrt{x - 2}$ - $\frac{3}{2}$$\sqrt{9x - 18}$ + 24$\sqrt{\frac{x - 2}{64}}$ = -17
$\Leftrightarrow $ $\frac{1}{2}$$\sqrt{x - 2}$ - $\frac{3}{2}$.3$\sqrt{x - 2}$ + 24.$\frac{1}{8}$$\sqrt{x - 2}$ = -17
$\Leftrightarrow $ $\frac{1}{2}$$\sqrt{x - 2}$ - $\frac{9}{2}$$\sqrt{x - 2}$ + 3$\sqrt{x - 2}$ = -17
$\Leftrightarrow $ - $\sqrt{x - 2}$ = -17
$\Leftrightarrow $ $\sqrt{x - 2}$ = 17
$\Leftrightarrow $ x - 2 = 289
$\Leftrightarrow $ x = 291
Vậy x = 291.
b) Ta có: - 5x + 7$\sqrt{x}$ + 12 = 0
$\Leftrightarrow $ - 5x - 5$\sqrt{x}$ + 12$\sqrt{x}$ + 12 = 0
$\Leftrightarrow $ - 5$\sqrt{x}$($\sqrt{x}$ + 1) + 12($\sqrt{x}$ + 1) = 0
$\Leftrightarrow $ ($\sqrt{x}$ + 1)(- 5$\sqrt{x}$ + 12) = 0
$\Leftrightarrow $ $\sqrt{x}$ + 1 = 0 hoặc - 5$\sqrt{x}$ + 12 = 0
$\Leftrightarrow $ $\sqrt{x}$ = - 1(vô nghiệm) hoặc $\sqrt{x}$ = $\frac{12}{5}$ $\Leftrightarrow $ x = $\frac{144}{25}$
Vậy x = $\frac{144}{25}$.