Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 2 - Nonlinear Functions - 2.4 Exponential Functions - 2.4 Exercises - Page 86: 27

Answer

$$ 27^{x} =9^{x^{2+x}} $$ The solution of the given equation is $$ x=0 \text { or } \quad x=\frac{1}{2}. $$

Work Step by Step

$$ 27^{x} =9^{x^{2+x}} $$ Since the bases must be the same, write 27as $3^{3 }$ and 9 as $ 3^{2} $ giving $$ \begin{aligned} 27^{x} &=9^{x^{2+x}} \\\left(3^{3}\right)^{x} &=\left(3^{2}\right)^{x^{2+x}} \\ 3^{3 x} &=3^{2 x^{2}+2 x} \\ 3 x &=2 x^{2}+2 x \\ 0 &=2 x^{2}-x \\ 0 &=x(2 x-1) \\ x=0 & \text { or } \quad 2 x-1=0 \\ x=0 & \text { or } \quad x=\frac{1}{2} \end{aligned} $$ So, the solution of the given equation is $$ x=0 \text { or } \quad x=\frac{1}{2}. $$
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