Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 5 - Polynomials and Factoring - 5.2 Factoring Trinomials of the Type x2+bx+c - 5.2 Exercise Set: 16

Answer

$(a-4)(a-5)$

Work Step by Step

The 2 numbers whose product is $ac= 1(20)=20 $ and whose sum is $b= -9 $ are $\left\{ -4,-5 \right\}.$ Using these two numbers to decompose the middle term of the given trinomial, $ a^2-9a+20 ,$ then the factored form is \begin{array}{l} a^2-4a-5a+20 \\\\= (a^2-4a)-(5a-20) \\\\= a(a-4)-5(a-4) \\\\= (a-4)(a-5) .\end{array}
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