Monday, May 18, 2015

College Algebra, Chapter 5, 5.4, Section 5.4, Problem 70

Solve the inequality $x^2 e^x - 2e^x < 0$

$
\begin{equation}
\begin{aligned}
x^2 e^x - 2e^x &< 0 \\
\\
x^2 e^x &< 2e^x && \text{Add } 2e^x\\
\\
\ln x^2 e^x &< \ln 2e^x && \text{Take ln of each side}\\
\\
\ln x^2 + \ln e^x &< \ln 2 + \ln e^x && \text{Properties of ln } \ln(AB) = \ln A + \ln B\\
\\
2 \ln x + x \ln e &< \ln 2 + x \ln e && \text{Properties of ln } \ln A^c = C\ln A\\
\\
2 \ln x &< \ln 2 && \text{Subtract } x \ln e\\
\\
\ln x &< \frac{\ln 2}{2} && \text{Divide by 2}\\
\\
e^{\ln x} &< e^{\frac{\ln 2}{2}} && \text{Raise } e \text{ to each side}\\
\\
x &< e^{\frac{\ln 2}{2}} && \text{Property of ln}
\end{aligned}
\end{equation}
$

No comments:

Post a Comment

Why is the fact that the Americans are helping the Russians important?

In the late author Tom Clancy’s first novel, The Hunt for Red October, the assistance rendered to the Russians by the United States is impor...