Toán Lớp 7: tính
|7x+5|=x-3x
|7x+5|=12-5x
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Toán Lớp 7: tính
|7x+5|=x-3x
|7x+5|=12-5x
Comments ( 2 )
$TH_{1}:$
$7x+5\geq0$ $(x\geq\dfrac{-5}{7})$
$⇔|7x+5|=7x+5$
$⇒7x+5=x-3x$
$⇔x-3x+7x=-5$
$⇔9x=-5$
$⇔x=\dfrac{-5}{9}$ $(TM)$
$TH_{2}:$
$7x+5<0$ $(x<\dfrac{-5}{7})$
$⇔|7x+5|=-7x-5$
$⇒-7x-5=x-3x$
$⇔-7x-x+3x=5$
$⇔-5x=5$
$⇔x=-1$ $(TM)$
Vậy $x=\dfrac{-5}{9};-1$
$TH_{1}:$
$7x+5\geq0$ $(x\geq\dfrac{-5}{7})$
$⇔|7x+5|=7x+5$
$⇒7x+5=12-5x$
$⇔7x+5x=12-5$
$⇔12x=7$
$⇔x=\dfrac{7}{12}$ $(TM)$
$TH_{2}:$
$7x+5<0$ $(x<\dfrac{-5}{7})$
$⇔|7x+5|=-7x-5$
$⇒-7x-5=12-5x$
$⇔-7x+5x=12+5$
$⇔-2x=17$
$⇔x=\dfrac{-17}{2}$ $(TM)$