Fill in the blanks to make a "perfect square." For example, in $$x^2 + 6x + \underline{\phantom{aaa}} = (x+\underline{\phantom{aaa}})^2$$ fill in $9$ and $3$ since $$x^2+6x + 9 = (x+3)^2.$$
$x^2 + 14x +$ $= (x +$ $)^2$.
$x^2 - 8x +$ $= (x -$ $)^2$.
$x^2 - 20x +$ $= (x -$ $)^2$.