CUET · MATHS · PYQ PAPER 2025
If \(\left|\begin{array}{ccc}1 & -2 & 5 \\ 2 & a & -1 \\ 0 & 4 & 2a\end{array}\right|=86\), then product of all values of \(a\) is :
- A 21
- B \(-21\)
- C 10
- D \(-4\)
Answer & Solution
Correct Answer
(B) \(-21\)
Step-by-step Solution
Detailed explanation
\( \left|\begin{array}{ccc}1 & -2 & 5 \\ 2 & a & -1 \\ 0 & 4 & 2a\end{array}\right| = 1(a(2a)-(-1)(4)) - (-2)(2(2a)-(-1)(0)) + 5(2(4)-a(0)) \) \( = (2a^2+4) + (8a) + (40) \) \( = 2a^2+8a+44 \) \( 2a^2+8a+44 = 86 \) \( 2a^2+8a-42 = 0 \) \( a^2+4a-21 = 0 \) Product of roots…
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