ok so set one side equal to zero by subtractin g7
now we have
y^2-2y-15=0
if we factor then set each factor to zero we can solve becasue if we have
xy=0 then assume x and y=0 so
y^2-2y-15
find what 2 factors of -15 add to -2
-5 and 3
(x-5)(x+3)
tada
(x-5)(x+3)=0
x-5=0
add 5
x=5
x+3=0
subtract 3
x=-3
x=5 or -3