Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 4 - Quadratic Functions - 4.7 Graphing Quadratics from Standard Form - 4.7 Exercises - Page 387: 33

Answer

A) Vertex :$(- 15.5,-264.5)$ B) Vertical intercept: $(0,216)$ Horizontal intercepts: $(4,0), (27,0)$ C) See the graph D) Domain: All real numbers. Range: $[-264.5,\infty )$

Work Step by Step

Given\begin{equation} \begin{aligned} g(s)&=2 s^2-62 s+216\\ a& = 2,\quad b= -62, \quad c= 216. \end{aligned} \end{equation} Step 1: Determine whether the graph opens up or down. The parabola opens up when the constant $a$ is positive and opens down when $a$ negative. This parabola opens up since $a$ is positive. Part A) Step 2: Find the vertex. This function is in standard form for a quadratic, so we can use the formula: \begin{equation} \begin{aligned} s & =\frac{-b}{2 a} \\ & =\frac{-(-62)}{2(2)} \\ & =15.5\\ g(15.5) & =2(15.5)^2-62(15.5)+216 \\ & =-264.5 \end{aligned} \end{equation} The vertex of the function is $(15.5,-264.5)$. Part B) Step 3: Find the vertical and horizontal intercepts. 1) Find the vertical intercept which equal to the constant $c$ if the parabola is in its standard form. \begin{equation} \begin{aligned} s& = 216 \end{aligned} \end{equation}Vertical intercept: $(0,216)$. 2) Find the horizontal intercept by setting the function to zero and solving for $s$. \begin{equation} \begin{aligned} &2s^2-62s+216=0\\ & s=\frac{-(-62)\pm\sqrt{(-62)^2-4(2)(216)}}{2 \cdot(2)} \\ & =\frac{62 \pm \sqrt{2116}}{4} \\ & =\frac{62 \pm 46}{4} \\ & =15.5 \pm 11.5\\ & s=15-11.5=4 \\ & s=15.5+11.5=27 \end{aligned} \end{equation} Horizontal intercepts: $(4,0), (27,0)$. Part C) sketch the graph as shown in the figure. Part D)The domain and range of the function are given below: Domain: All real numbers. Range:$[-264.5,\infty )$
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