Here's a physics problem. I don't care about the answer, i just want to know how to do it. don't have to be too detailed.. but i don't really kno how to start this

Question

1.) A model rocket blasts off from the ground rising straight upward with a constant acceleration that has a magnitude of 86 m/s^2 for 1.70 seconds, at which point fuel runs out. Air resistance neglected What maximum altitude will the rocket reach?
What I did: okay. so regarding number 1. I will use the first method. So I will calculate using this formula?

x = v0t + 1/2at^2,

in which case.. x = 86(1.70) + 1/2(-10)(1.70)^2? I get x, which would be the position.. how do figure out the height over initial velocity? do i plug 0 in for v0?

Answer 1

Where did you get Vo as 86?
where did you get acceleration as -10?