Functions Modeling Change: A Preparation for Calculus, 5th Edition

Published by Wiley
ISBN 10: 1118583191
ISBN 13: 978-1-11858-319-7

Chapter 3 - Quadratic Functions - 3.2 The Vertex of a Parabola - Exercises and Problems for Section 3.2 - Exercises and Problems - Page 127: 16

Answer

Standard form: $g(s)=2 s^2-7 s-15$ Vertex form: $g(s)=2\left(s-\frac{7}{4}\right)^2-\frac{169}{8}$ Factored form: $g(s)=2(s-5)\left(s+\frac{3}{2}\right)$.

Work Step by Step

16)The standard form is : $$ g(s)=(s-5)(2 s+3)=2 s^2+3 s-10 s-15=2 s^2-7 s-15 $$ Complete the square to get the vertex form. $$ \begin{aligned} g(s) & =2 s^2-7 s-15 \\ & =2\left(s^2-\frac{7}{2} s-\frac{15}{2}\right) \\ & =2\left(s^2-\frac{7}{2} s+\left(\frac{7}{4}\right)^2-\left(\frac{7}{4}\right)^2-\frac{15}{2}\right) \\ & =2\left(s-\frac{7}{4}\right)^2+2\left(-\frac{49}{16}-\frac{120}{16}\right) \\ & =2\left(s-\frac{7}{4}\right)^2-\frac{169}{8} \end{aligned} $$ The factored form is $$ g(s)=(s-5)(2 s+3)=2(s-5)\left(s+\frac{3}{2}\right) $$
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