Solve the following equation for $x$x by factoring or otherwise:
$x^2+4x-21=0$x2+4x−21=0
Write all your solutions on the same line, separated by a comma.
Solve the following equation for $x$x:
$x^2+10x+16=0$x2+10x+16=0
Solve the following equation for $x$x:
$x^2+7x-18=0$x2+7x−18=0
Solve the following equation for $x$x:
$x^2-20x+99=0$x2−20x+99=0