Complete the square to find the vertex of this parabola

the rocket cannot penetrate the ground, in a contextual sense, therefore the roots of this equation should be the domain of this function. i'll let you find the roots of this quadratic equation (hint: use the quadratic formula:  

1- c

2-a

step-by-step explanation:

mark brainliest!

the answer to this in exact form is 4/35 but in decimal form its 0.1142857

hope this if needed hmu