Solution
To find the values of t for which the ball's height is 2 meters
we set h = 2
=> 2 = 1 + 7t - 5t^2
=>5t^2 - 7t + 1 = 0
Using the quadratic formula,
[tex]\begin{gathered} t=\frac{-b\pm\sqrt{b^2-4ac}}{2a} \\ \\ \Rightarrow t=\frac{7\pm\sqrt{\left(-7\right)^2-4\left(5\right)\left(1\right)}}{2\cdot5} \\ \\ \Rightarrow t=1.24s\text{ or }0.16s \end{gathered}[/tex]Therefore, t = 1.23s or 0.16s
