The answer to the problem is
y=1/2x
The zero product property tells us that if we have
xy=0, then we can assume that x and y both equal 0
so
(4k+5)(k+7)=0
we can assume that 4k+5=0 and k+7=0
so
4k+5=0
minus 5 both sides
4k=-5
divide both sides by 4
k=-5/4
k+7=0
minus 7 both sides
k=-7
k=-5/4 or -7
Hope this helps! I can’t help with the graphing...