# Chapter P - Prerequisites: Fundamental Concepts of Algebra - Exercise Set P.1: 20

The ball's height 3 seconds after it was kicked was 40 feet.

#### Work Step by Step

A football was kicked vertically upward from a height of 4 feet with an initial speed of 60 feet per second. The formula $$h=4+60t−16t^{2}$$ describes the ball's height above the ground, h, in feet, t seconds after it was kicked. What was the ball's height 3 seconds after it was kicked? 2 seconds represents the time, t, so substitute the 3 for each t in the equation:$$h=4+60(3)−16(3)^2$$ Work exponents first:$$h=4+60(3)−16(9)$$ Figure all division and multiplication next (in order left to right):$$h=4+180−144$$ Then complete all addition and subtraction in order left to right:$$h=184−144$$ $$h=40$$

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