Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 4 Quadratic Functions and Factoring - 4.7 Complete the Square - 4.7 Exercises - Skill Practice - Page 289: 57


The solutions are $-\displaystyle \frac{1}{2}+i\frac{\sqrt{19}}{2}$ and $-\displaystyle \frac{1}{2}-i\frac{\sqrt{19}}{2}$.

Work Step by Step

$ 0.4v^{2}+0.7v=0.3v-2\qquad$ ...write the expression in the form $ax^{2}+bx=c$ (add $-0.3v$ to each side) $ 0.4v^{2}+0.4v=-2\qquad$ ...multiply the entire expression with $10$. $ 4v^{2}+4v=-20\qquad$ ...divide each term with $4$. $ v^{2}+v=-5\qquad$ ...square half the coefficient of $v$. $(\displaystyle \frac{1}{2})^{2}=\frac{1}{4}\qquad$ ...complete the square by adding $\displaystyle \frac{1}{4}$ to each side of the expression $ v^{2}+v+\displaystyle \frac{1}{4}=-5+\frac{1}{4}\qquad$ ...Write $v^{2}+v+\displaystyle \frac{1}{4}$ as a binomial squared. $(v+\displaystyle \frac{1}{2})^{2}=-\frac{19}{4}\qquad$ ...take square roots of each side. $ v+\displaystyle \frac{1}{2}=\pm\sqrt{-\frac{19}{4}}\qquad$ ...simplify $\displaystyle \sqrt{-\frac{19}{4}}=i\sqrt{\frac{19}{4}}=i\frac{\sqrt{19}}{2}$ $ v+\displaystyle \frac{1}{2}=\pm i\frac{\sqrt{19}}{2}\qquad$ ...add $-\displaystyle \frac{1}{2}$ to each side. $v=-\displaystyle \frac{1}{2}\pm i\frac{\sqrt{19}}{2}$
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