Mujib has factorised correctly. Mujib and I both assumed that you were asked to factorise, maybe you were asked to graph? Thinking about it that is probably moe likely but you have to start the same way anyway.
Your problem was
y=x 2+2x-15
so
y= 2+2x-15
To factorise you need to look for 2 numbers
that multiply together to give -15
and add together to give 2
(3 and 5 might be worth looking at)
Since they multiply to give a negative number, one is pos and the other neg
Since they add to a positive, the bigger number is the positive one.
so, 5 and -3 work
hence
y=(x+3)(x-2)
+118667 
