Question 69181
You did fine as far as you went so let's continue from where you left off:
{{{y^2-4 = 4y-4}}} Add 4 to both sides of the equation.
{{{y^2 = 4y}}} Subtract 4y from both sides.
{{{y^2-4y = 0}}} Factor a y on the left side.
{{{y(y-4) = 0}}} Apply the zero product principle.
{{{y = 0}}} and/or {{{y-4 = 0}}}
The solutions are:
{{{y = 0}}}
{{{y = 4}}}