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 - Chapter Review Exercises - Page 401: 57

Answer

$(1,13),(4.5,118)$

Work Step by Step

Given \begin{equation} \begin{aligned} & y=6 x^2-3 x+10 \\ & y=4 x^2+8 x+1. \end{aligned} \end{equation} Set the two equations equal and find the values of $x$. Use the values of $x$ to find the corresponding values of $y$ and write the solutions as points, $(x,y)$.\begin{equation} \begin{aligned} 6 x^2-3 x+10&=4 x^2+8 x+1 \\ 6 x^2-4 x^2-3 x-8 x+10-1&=0 \\ 2 x^2-11 x+9&=0. \end{aligned} \end{equation} Use factoring: \begin{equation} \begin{aligned} 2 x^2-9 x-2 x+9&=0 \\ x(2 x-9)-1(2 x-9)&=0 \\ (2 x-9)(x-1)&=0. \end{aligned} \end{equation} This gives \begin{equation} \begin{array}{r} 2 x-9=0 \\ x=\frac{9}{2}=4.5 \\ x-1=0 \\ x=1. \end{array} \end{equation} The corresponding $y$ values are: \begin{equation} \begin{aligned} & y=4(4.5)^2+8(4.5)+1=118 \\ & y=4(1)^2+8(1)+1=13. \end{aligned} \end{equation} Solution: $$(1,13),(4.5,118).$$
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