How do you solve $3x² = 21$ ?

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Answer 1 · 2015-06-24T14:33:52

$color(green)( x = +sqrt7$
$color(green)( x = -sqrt7$

$3x² = 21$

$3x² - 21=0$
Here $3$ is common to both terms:

$3(x² - 7)=0$

$x² - 7=0$

$x² = 7$
$x = +-sqrt7$

The solutions are:
$color(green)( x = +sqrt7 , x = -sqrt7$

How do you solve 3x² = 213x² = 21?