Chapter 5: Exercises with Solutions

Section 5.4The Quadratic Formula(a)(b)Lastly, to find the y-intercept, set x = 0 in the equation and solve for y:f(x) = −2x 2 + 16x + 8f(0) = −2(0) 2 + 16(0) + 8f(0) = 8So the y-intercept is (0, 8).Finally, put this all together to make the graph.50y(4,40)((−16+ √ (0,8) (8,8)320)/(−4),0)((−16− √ 320)/(−4),0)x20x=4f(x)=−2(x−4) 2 +40To find the domain of f, mentally project every point of the graph onto the x-axis, asshown on the left below. This covers the entire x-axis, so the domain= (−∞, ∞). Tofind the range, mentally project every point of the graph onto the y-axis, as shown onthe right below. The shaded interval on the y-axis is range= (−∞, 40].Version: Fall 2007