y^2 -21y+90=0 Factor and solve

y^2 -21y+90=0

(y )(y ) ( -15)( -6)=0

(y-15) (y-6) = 0

Solve:

(y-15) =0

y-15+15 =0+15

y=15

Solve:

(y-6) = 0

y-6+6 = 0+6

y=6