Question

gải thương trình ?

cân bậc 9x-45+cân bậc 4x-20-cân bậc x-5=8

Answer 1

`sqrt(9x-45) + sqrt(4x-20) - sqrt(x-5) = 8`

Đk: `x >=5`

`<=> 3sqrt(x-5) + 2sqrt(x-5) - sqrt(x-5) = 8`

`<=> 4 sqrt(x-5) = 8`

`<=> sqrt(x-5)  = 2`

`=> x - 5 = 4`

`=> x = 9`

Answer 2

`\sqrt{9x-45}+\sqrt{4x-20}-\sqrt{x-5}=8`    `ĐK: x >= 5`

`<=>\sqrt{3^2(x-5)}+\sqrt{2^2(x-5)}-\sqrt{x-5}=8`

`<=>3\sqrt{x-5}+2\sqrt{x-5}-\sqrt{x-5}=8`

`<=>4\sqrt{x-5}=8`

`<=>\sqrt{x-5}=2`

`<=>x-5=4`

`<=>x=9` (t/m)

Vậy `S={9}`

Answer 3

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