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JEE Main 202324 JanuaryEvening Shift
Exam
JEE Main
Year
2023
Date
24 January
Shift
Evening Shift
Subject
Mathematics
Chapter
Determinants

JEE Main 2023 · 24 January · Evening Shift · Mathematics · Determinants

If the system of equations x + 2y + 3z = 3 , 4x + 3y - 4z = 4 and...

If the system of equations x+2y+3z=3x + 2y + 3z = 3, 4x + 3y - 4z = 4 and 8x+4y−\lambdaz=9+μ8x + 4y - \lambdaz = 9 + \mu has infinitely many solutions, then the ordered pair (λ,μ)\left(\lambda, \mu\right) is equal to

Options

  1. A(725,215)\left(\dfrac{72}{5}, \dfrac{21}{5}\right)
  2. B(−725,−215)\left(\dfrac{- 72}{5}, \dfrac{- 21}{5}\right)
  3. C(725,−215)\left(\dfrac{72}{5}, \dfrac{- 21}{5}\right)
  4. D(−725,215)\left(\dfrac{- 72}{5}, \dfrac{21}{5}\right)

Correct answer

C. (725,−215)\left(\dfrac{72}{5}, \dfrac{- 21}{5}\right)

Step-by-step solution

Given,

The system of equations

x+2y+3z=3......(1)</p><p>x + 2y + 3z = 3 . . . . . . \left(1\right)</p><p>4x + 3y - 4z = 4 . . . . . . . . . \left(2\right)</p><p></p><p>8x + 4y - \lambdaz = 9 + \mu . . . . . \left(3\right)

Now usingthetheoperation, equation \left(1\right) \times 4 - \left(2\right) we get,

5y+16z=8........(4)5y + 16z = 8 . . . . . . . . \left(4\right)

Now using the operation, equation \left(2\right)×2−(3)\times 2 - \left(3\right) we get,

2y+(λ−8)2y + \left(\lambda - 8\right)z = - 1 - \mu . . . . . . . . \left(5\right)</p><p>Nowusingtheoperation,equation(4)</p><p>Now using the operation, equation \left(4\right) \times 2 - \left(3\right)×5\times 5 we get,

\left(72 - 5\lambda\right)z = 21 + 5\mu</p><p>Nowgivensystemofequationhasinfinitelymanysolutions,somakingcoefficientof</p><p>Now given system of equation has infinitely many solutions, so making coefficient ofztobezeroandequatingto be zero and equating21 + 5\muwithzeroweget,</p><p>with zero we get,</p><p>72 - 5\lambda = 0 ⇒ \lambda = \dfrac{72}{5} andnd21 + 5\mu = 0 ⇒ \mu =\dfrac{- 21}{5}</p><p>Hence,theorderedpair(λ,μ)</p><p>Hence, the ordered pair \left(\lambda, \mu\right) is equal to \left(\dfrac{72}{5}, \dfrac{- 21}{5}\right)$.

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