Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 2 - Section 2.7 - Combining Functions - 2.7 Exercises - Page 217: 74

Answer

$f(x)=x^{2}+6$ $g(x)=x^{2}+x-1$

Work Step by Step

First problem: Squaring g(x), ... $[g(x)]^{2}=4x^{2}+4x+1,$ so we need to add 6 to this and we have h(x). Our function f will "square the number and add 6", that is $f(x)=x^{2}+6$ In the second problem, we search for g(x) such that $f(g(x))=h(x),$ $3[g(x)]+5=3x^{2}+3x+2$ Equality of polynomials $\Rightarrow$ equate the coefficients. g is quadratic, and the leading coefficient is 1. g(x)$=x^{2}+bx+c$ From $3c+5 $(off the left side) being equal to 2 (on the right side), we find $c=-1,$ so, $g(x)=x^{2}+bx-1$ Since 3b must equal 3, it follows that b=1. So, $g(x)=x^{2}+x-1$ Check: $f(g(x))=3(x^{2}+x-1)+5=3x^{2}+3x+2=h(x)$
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