Given:
[tex]h=2+15t-5t^2[/tex]Let the height of the ball is 7 meteres.
h=7,
[tex]7=2+15t-5t^2[/tex][tex]5t^2-15t-2+7=0[/tex][tex]5t^2-15t+5=0[/tex][tex]t^2-3t+1=0[/tex][tex]t=\frac{3\pm\sqrt[]{3^2-4(1)(1)}}{2(1)}[/tex][tex]t=\frac{3\pm\sqrt[]{9-4}}{2}[/tex][tex]t=\frac{3\pm\sqrt[]{5}}{2}[/tex][tex]t=\frac{3+\sqrt[]{5}}{2},\frac{3-\sqrt[]{5}}{2}[/tex][tex]t=\frac{3+2.24}{2},\frac{3-2.24}{2}[/tex][tex]t=\frac{5.24}{2},\frac{0.76}{2}[/tex][tex]t=2.62,0.38[/tex]The ball in the height of 7 meters at 0.38 seconds and 2.62 seconds.
