Quadratic Equations... Problem Solving
A ball is thrown straight up. Its height, h(in metres), after t seconds is give by h= -5t^2+10t+2. To the nearest tenth of a second, when is the ball 6m above the ground? Explain why there are two answers.
I don't know how to manipulate the formula and how to solve for this problem.
Second question,
The period of a pendulum is the time it takes to swing back and forth, returning to its original position. The relationship between the period, T(in seconds), and the length of the pendulum, L(in metres) is as follows,
T^2 - 4L=0
Correct to the nearest tenth of a second, what is the period of a pendulum 3m long?
Do you use factoring and how?
Thank you.