2A rocket is fired down a practice range. The height of the rocket in metres after t seconds is given by h = -1/4t² + 3t + 45. Find the maximum height attained by the
rocket.​

(C) 16

Step-by-step explanation:

Subtract the second equation from the first equation.

9x + 2y^2 - 3z^2 = 132 minus 9y + 2y^2 - 3z^2 = -12

                            9x + 2y^2 - 3z^2 = 132

                            -(9y + 2y^2 - 3z^2 = -12 )  

This will change all the signs of the second equation.

9x + 2y^2 - 3z^2 = 132

-9y - 2y^2 + 3z^2 = +12

You have left 9x - 9y = 144.

Factor out the 9 so you have 9(x - y) = 144

Divide both sides by 9

x - y = 16