15 - 2(- 13s + 3) = 9s - 9 + 16s
15 + 26s - 6 = 25s - 9
9 + 26s = 25s - 9
26s - 25s = -9 - 9
s = - 18
Answer:

Step-by-step explanation:
Completing the square gives

So we have to cancel the latter two terms out for the expression to always become a square (otherwise we are dealing with a square plus something else, which doesn't always result in a square), giving us our answer directly.
Yes - it goes through the origin when graphed.