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Question: Answered & Verified by Expert
- If $p$ and $q$ are prime numbers satisfying the condition $p^{2}-2 q^{2}=1$, then the value of $p^{2}+2 q^{2}$ is
MathematicsBasic of MathematicsCOMEDKCOMEDK 2019
Options:
  • A 5
  • B 15
  • C 16
  • D 17
Solution:
1254 Upvotes Verified Answer
The correct answer is: 17
We have,
$$
p^{2}-2 q^{2}=1
$$
Let $p=3, q=2$
$$
\begin{array}{ll}
\text { Then, } & p^{2}-2 q^{2} \\
& =(3)^{2}-2(2)^{2}=9-8=1 \\
\therefore \quad & p^{2}-2 q^{2}=1
\end{array}
$$
Now, $p^{2}+2 q^{2}=(3)^{2}+2(2)^{2}$
$$
=9+8=17
$$

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