A) 12 m/s/3 seconds, 4 m/s/1s = 4 m/s^2
b) -12 m/s in 4 seconds = -3 m/s^2
c) 18+7*12=102 meters
The sum of the squared legs must give the squared hypotenuse:

But of course we can only accept the positive solution, because
is a length and can't be negative.
y = x^2+5x-6 is the answer.