CAT 2024 Quant was dominated by Algebra followed by Arithmetic. In Arithmetic, the questions were dominated by topics like Speed-time-distance, Mixture and Alligations. This year, there was a surprise. The questions from Geometry were relatively on the lower side as compared to the previous years. There were 8 TITA Qs this year. Overall this section was at a medium level of difficulty.
Question 22 The sum of all distinct real values of \(x\) that satisfy the equation \(10^x+\frac{4}{10^x}=\frac{17}{2}\), is
Let \(10^x=y\)
Then, \(y+\frac{4}{y}=\frac{17}{2}\)
\[
2 y^2-17 y+8=0
\]
After factorising the equation we get, \((2 y-1)(y-8)=0\)
i.e., \(y=8\) or \(y=1 / 2\)
\[
\Rightarrow 10^x=8 \text { or } 10^x=1 / 2
\]
Taking log on both sides, we get
\[
\begin{array}{lrc}
\log _{10} 8=x & \text { or } & \log _{10} 1 / 2=x \\
\Rightarrow \log _{10} 2^3=x & \text { (or) } & \log _{10} 2^{-1}=x \\
\Rightarrow x=3 \log _{10} 2 & \text { (or) } & x=-\log _{10} 2
\end{array}
\]
Sum of these possible values \(=3 \log _{10} 2+\left(-\log _{10} 2\right)=2 \log _{10} 2\)
The question is "The sum of all distinct real values of \(x\) that satisfy the equation \(10^x+\frac{4}{10^x}=\frac{17}{2}\), is"
Choice A is the correct answer.
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