Đáp án:
`text{a,x = 225}`
`text{b,x = 49}`
`text{c,0 ≤ x < 2}`
Giải thích các bước giải:
$a)\sqrt{x}=15$
$⇔(\sqrt{x})^2=15^2$
$⇔x=225$
$b)2\sqrt{x}=14$
$⇔\sqrt{x}=7$
$⇔\sqrt{x}^2=7^2$
$⇔x=49$
$c)\sqrt{x}<\sqrt{2}$
$⇔x<2$
$d)\sqrt{2x}<4$
$⇔\sqrt{2x}<\sqrt{16}$
$⇔2x<16$
$⇔x<8$
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