Question

How to factor (y-3)(y+4)=30

Answer 1

$(y-3)(y+4)= 30$ then you have $y^2+4y-3y-12=30$ ⇔ $y^2+y-42=0$ ⇔ $(y+7)(y-6)=0$

Answer 2

so first you expand
use foil or whatever
y²-3y+4y-12=30
y²+y-12=30
minus 30 from both sides
y²+1y-42=0
factor
what 2 numbers multiply to -42 and add to 1?
-6 andn 7
(y-6)(y+7)=0
set each to zero

y-6=0
y=6

y+7=0
y=-7

y=-7 or 6