Question

Solve the following equation using the general formula:
$\frac{x^2-1}{x^2+1}=\frac{4}{5}$

Answer 1

$\frac{x^2-1}{x^2+1}=\frac{4}{5}$

$\Rightarrow 5(x^2-1)=4(x^2+1)$

$\Rightarrow 5x^2-5=4x^2+4$

$x^2=9$

$x=\pm 3$.