`a) 5\sqrt{x} - 2 = 13` đkxd : `x≥0`
`⇒5\sqrt{x} = 15`
`⇒\ sqrt{x} = 15:5`
`⇒\sqrt{x} = 3`
`⇒x =3^2 =9` ( thỏa mãn)
`b) 2\sqrt{8x} + 7\sqrt{18x} = 9- \sqrt{50x}` đkxd : `x≥0`
`⇒2\sqrt{2^2 .2x} + 7\sqrt{3^2 .2x} = 9-\sqrt{5^2 .2x}`
`⇒4\sqrt{2x} + 21\sqrt{2x} = 9 - 5\sqrt{2x}`
`⇒30\sqrt{2x} =9`
`⇒\sqrt{2x} = 9/30`
`⇒2x = 81/ 900`
`⇒x = 9/200`( thỏa mãn)
#hoctot