Answer:
2.9437 seconds
Step-by-step explanation:
I assume that you made a typo and the equation is -167s² + 16s + 1400
Find the zeros of the equation, or where it crosses the x-axis, to find at what time the pebble hits the ground. At these points, the height will be 0.
Use the quadratic equation
[tex]\frac{-16 + \sqrt{16^{2} -4(-167)(1400)} }{2(-167)}[/tex] = -2.8479
[tex]\frac{-16 - \sqrt{16^{2} -4(-167)(1400)} }{2(-167)}[/tex] = 2.9437
The negative answer doesn't make sense since time (s) starts from 0 and must be postive. Therefore, the answer is 2.9437