Calculate the following limits$.$ For a number, write and integer $($for example, $2$ or $-2)$ or a reduced fraction $($for exomple, $3/7$ or $-3/7)$; for $,$ write INF; for $-,$ write $-$INF.

$\underset{x1}{lim}\frac{x^2-1}{x^{2}x-2}=$

$\underset{x}{lim}\frac{2x^{2}2x3}{5x^2-x-2}=$

$\underset{x-}{lim}\frac{-x^{4}2x^2-3}{2x^{2}x5}=$

$\underset{x0}{lim}\frac{tanx}{2x}=$