Introductory Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-805-X
ISBN 13: 978-0-13417-805-9

Chapter 6 - Section 6.6 - Solving Quadratic Equations by Factoring - Exercise Set - Page 473: 13


x=-3 or 7

Work Step by Step

Rewrite the equation in standard form. x$^2$-4x=21 x$^2$-4x-21=0 Factor the trinomial. (x+3)(x-7)=0 Set each variable factor as equal to zero and then isolate the variable to find the solutions. x+3=0 or x-7=0 x=-3 or x=7 Enter the original equation into your graphing utility to observe that the graph crosses the x-axis at -3 and 7.
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