Question

Giải phương trình sau:

12: \(\sqrt{5x-4}=2\sqrt{5}\)

13: \(\sqrt{9.\left(x^2-2x+1\right)}=12\)

14: \(3x-\sqrt{9x^2+6x+1}=2x-3\)

15: 5+\(\sqrt{4x^2-12+9}+x=3x-2\)

mn giải giúp e với ạ

Answer 1

`12)\sqrt{5x-4}=2\sqrt{5}`     `ĐK: x >= 4/5`

`<=>5x-4=20`

`<=>x=24/5` (t/m)

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`13)\sqrt{9(x^2-2x+1)}=12`

`<=>3\sqrt{(x-1)^2}=12`

`<=>|x-1|=4`

`<=>[(x-1=4),(x-1=-4):}<=>[(x=5),(x=-3):}`

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`14)3x-\sqrt{9x^2+6x+1}=2x-3`    `ĐK: x >= -3`

`<=>\sqrt{(3x+1)^2}=x+3`

`<=>|3x+1|=x+3`

`<=>[(3x+1=x+3),(3x+1=-x-3):}<=>{(x=1),(x=-1):}`   (t/m)

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`15)5+\sqrt{4x^2-12x+9}+x=3x-2`     `ĐK: x >= 7/2`

`<=>\sqrt{(2x-3)^2}=2x-7`

`<=>|2x-3|=2x-7`

`<=>[(2x-3=2x-7),(2x-3=7-2x):}<=>[(0x=-4(Vô lí)),(x=5/2(ko t//m)):}`

  `=>` Ptr vô nghiệm