Algebra 1 Word Problem

Question

If a ball is thrown vertically upward with an initial speed of 39 feet per second, its height in feet above the ground t seconds later is given by the formula h = 39t-16t^2. At how many seconds will the ball be 10 feet above the ground? Give both answers and round to the nearest hundredth.

Answer 1

10 = 39t - 16t²

Remember that the quadratic formula tacitly assumes that the coefficient of the squared term is positive.

The formula gives (39 ± sqrt(881)0/32...and both answers are relevant! You can do the arithmetic!