√x-3 + √25x-75 -1/3 √9x-27 =30

2 câu trả lời

Lời giải:

`\sqrt{x-3}+\sqrt{25x-75}-1/(3).\sqrt{9x-27}=30`  (ĐKXĐ : `x≥3`)

`⇔\sqrt{x-3}+\sqrt{25.(x-3)}-1/(3).sqrt{9.(x-3)}=30`

`⇔\sqrt{x-3}+5\sqrt{x-3}-\sqrt{x-3}=30`

`⇔5\sqrt{x-3}=30`

`⇔\sqrt{x-3}=6`

`⇔x-3=6^2`

`⇔x-3=36`

`⇔x=36+3`

`⇔x=39` (Thỏa mãn ĐKXĐ)

Vậy `S={39}`

`#tnvt`

`\sqrt{x-3}+\sqrt{25x-75}-1/3\sqrt{9x-27}=30(x>=3)`

`<=>\sqrt{x-3}+\sqrt{25(x-3)}-1/3\sqrt{9(x-3)}=30`

`<=>\sqrt{x-3}+5\sqrt{x-3}-\sqrt{x-3}=30`

`<=>5\sqrt{x-3}=30`

`<=>\sqrt{x-3}=6`

`=>x-3=36`

`<=>x=39(tm)`

Vậy `x=39`

 

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