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JEE Main 202118 MarchEvening Shift
Exam
JEE Main
Year
2021
Date
18 March
Shift
Evening Shift
Subject
Mathematics
Chapter
Determinants

JEE Main 2021 · 18 March · Evening Shift · Mathematics · Determinants

Let the system of linear equations 4x + + 2z = 0 2x - y + z = 0 +...

Let the system of linear equations
4x+\lambday+2z=04x + \lambday + 2z = 0
2x−y+z=02x - y + z = 0
\mux+2y+3z=0,λ,μ∈R\mux + 2y + 3z = 0, \lambda, \mu \in R
has a non-trivial solution. Then which of the following is true?

Options

  1. Aμ=6,λ∈R\mu = 6, \lambda \in R
  2. Bλ=2,μ∈R\lambda = 2, \mu \in R
  3. Cλ=3,μ∈R\lambda = 3, \mu \in R
  4. Dμ=−6,λ∈R\mu = - 6, \lambda \in R

Correct answer

A. μ=6,λ∈R\mu = 6, \lambda \in R

Step-by-step solution

For non-trivial solution

\left|\begin{cases}4 & \lambda & 2 \\ 2 & - 1 & 1 \\ \mu & 2 & 3\end{cases}\right| = 0

⇒−20−6λ+λμ+8+2μ=0⇒ - 20 - 6\lambda + \lambda\mu + 8 + 2\mu = 0

⇒2μ−6λ+λμ=12⇒ 2\mu - 6\lambda + \lambda\mu = 12

when μ=6,12−6λ+6λ=12\mu = 6, 12 - 6\lambda + 6\lambda = 12

which is satisfied by all λ\lambda

When λ=2,4μ=24\lambda = 2, 4\mu = 24

When λ=3,5μ=30\lambda = 3, 5\mu = 30

When μ=−6,−12−6λ−6λ=12\mu = - 6, - 12 - 6\lambda - 6\lambda = 12

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