If (2 p+1/p)=4, the value of (p³+1/(8 p³)) is · ABC26GN1277
Subject: General Aptitude · Chapter: Simplification · Exam: S.S.C. 2010
If $\left(2 p+\frac{1}{p}\right)=4$, the value of $\left(p^{3}+\frac{1}{8 p^{3}}\right)$ is
Answer
Explanation
$$\begin{aligned} \left(2 p+\frac{1}{p}\right)=4 & \Rightarrow \frac{1}{2}\left(2 p+\frac{1}{p}\right)=\frac{1}{2} \times 4 \Rightarrow\left(p+\frac{1}{2 p}\right)=2 \\ & \Rightarrow\left(p+\frac{1}{2 p}\right)^{3}=2^{3}=8 \\ & \Rightarrow p^{3}+\frac{1}{8 p^{3}}+3 p \cdot \frac{1}{2 p}\left(p+\frac{1}{2 p}\right)=8 \\ & \Rightarrow p^{3}+\frac{1}{8 p^{3}}+3 \times \frac{1}{2} \times 2=8 \\ & \Rightarrow p^{3}+\frac{1}{8 p^{3}}=8-3=5 \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.
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