Question
If $\log (x^2- 21) = 2,$ show that $x =± 11.$
✓
Answer
$ \log \left(x^2-21\right)=2 $
$\Rightarrow x^2-21=10^2 $
$\Rightarrow x^2-21=100 $
$\Rightarrow x^2=121 $
$\Rightarrow x= \pm 11$
$\Rightarrow x^2-21=10^2 $
$\Rightarrow x^2-21=100 $
$\Rightarrow x^2=121 $
$\Rightarrow x= \pm 11$
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