Tìm x biết sqrt(64x-64)-sqrt(25x+25)+sqrt(4x+4)=20

`\sqrt{64x-64}-\sqrt{25x+25}+\sqrt{4x+4}=20`

`ĐK :` `x` $\ge $ 1

$\Leftrightarrow$ `8.\sqrt{x-1}-5.\sqrt{x+1}+2.\sqrt{x+1}=20`

$\Leftrightarrow$ `(-5+2).\sqrt{x+1}=20-8\sqrt{x-1}`

$\Leftrightarrow$ `(3.\sqrt{x+1})^2=(20-8\sqrt{x-1})^2`

$\Leftrightarrow$ `9x+9=400-320\sqrt{x-1}+64x-64`

$\Leftrightarrow$ `320\sqrt{x-1}=400-9x-9+64x-64`

$\Leftrightarrow$ `320\sqrt{x-1}=55x+327`

$\Leftrightarrow$ `102400x-102400=3025x^2+35970x+106929`

$\Leftrightarrow$ `3025x^2-66430x+209329`

$\Leftrightarrow$ `x_1 ~~ 18,15(TM)` hoặc `x_2 ~~ 3,81(TM)`