The height, h, in meters, of a football t seconds after being thrown is given by the formula: $h = 30 t - 5 t^{2}$ $h = 30t - 5t^2$ . How long after being thrown is the ball at a height of 25 meters?

Question

3231 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-11-24T21:32:38

Replace h with 25m.

$25 = 30 t - 5 t^{2}$ $25 = 30t - 5t^2$

Rearrange it

$- 5 t^{2} + 30 t - 25 = 0$ $-5t^2 + 30t -25 = 0$

Facotorization and Simplification

$- 5 (t^{2} - 6 t + 5) = 5 (t - 5) (t - 1)$ $-5 ( t^2 -6t + 5) = 5(t-5)(t-1)$

Find t

$(t - 5) = 0, t = 5$ $(t-5)=0, t = 5$
$(t - 1) = 0, t = 1$ $(t-1)=0, t = 1$

Has a height of 25 at 1 s and 5 s

The height, h, in meters, of a football t seconds after being thrown is given by the formula: h=30t−5t2h = 30t - 5t^2. How long after being thrown is the ball at a height of 25 meters?