Question

Noelle stands at the edge of a cliff and drops a rock. The height of the rock, in meters, is given by the function f(x)=−4.9x^2+17 , where x is the number of seconds after Noelle releases her rock. Cesar, who is standing nearby on the ground, throws a rock straight up in the air. The height of Cesar’s rock, in meters, is given by the function g(x)=−4.9x^2+13x , where x is the number of seconds after he releases his rock. There is a moment when the rocks are at the same height.

Answer 1

The best way to solve questions like this is to plug them into the "desmos graphing calculator". It literally draws you your graph. For this question, the answer is :
The rocks are at the same height at x = 1.308

Hope this helps!