Giải pt:
$-\sqrt{2-x}(3x+5)-5\sqrt{2+x}=0$
-$\sqrt{2-x}$ ( 3x + 5) - 5$\sqrt{2+x}$ = 0
$\Leftrightarrow$ $\sqrt{2-x}$( 3x + 5) = -5$\sqrt{2+x}$
$\Leftrightarrow$ ( 3x + 5)2( 2 -x ) = 25 ( 2 + x)
$\Leftrightarrow$ ( 9x2 + 30x + 25 )( 2-x ) = 50 + 25x
$\Leftrightarrow$ 18x2 + 60x + 50 - 9x3 - 30x2 - 25x = 50 + 25x
$\Leftrightarrow$ -9x3 - 12x2 + 10x = 0
$\Leftrightarrow$ 9x3 + 12x2 - 10x = 0
$\Leftrightarrow$ x $\epsilon$ { 0 ; $\frac{-2-\sqrt{14}}{3}$ ; $\frac{-2+\sqrt{14}}{3}$ }
Giải pt:
$-\sqrt{2-x}(3x+5)-5\sqrt{2+x}=0$
-$\sqrt{2-x}$ ( 3x + 5) - 5$\sqrt{2+x}$ = 0
$\Leftrightarrow$ $\sqrt{2-x}$( 3x + 5) = -5$\sqrt{2+x}$
$\Leftrightarrow$ ( 3x + 5)2( 2 -x ) = 25 ( 2 + x)
$\Leftrightarrow$ ( 9x2 + 30x + 25 )( 2-x ) = 50 + 25x
$\Leftrightarrow$ 18x2 + 60x + 50 - 9x3 - 30x2 - 25x = 50 + 25x
$\Leftrightarrow$ -9x3 - 12x2 + 10x = 0
$\Leftrightarrow$ 9x3 + 12x2 - 10x = 0
$\Leftrightarrow$ x $\epsilon$ { 0 ; $\frac{-2-\sqrt{14}}{3}$ ; $\frac{-2+\sqrt{14}}{3}$ }
Chỗ này bạn thiếu điều kiện $3x+5\leq 0\Leftrightarrow x\leq -\frac{5}{3}$
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