Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Advanced 2021Paper 1
Exam
JEE Advanced
Year
2021
Paper
Paper 1
Subject
Mathematics
Chapter
Determinants

JEE Advanced 2021 · Paper 1 · Mathematics · Determinants

Let α, β and γ be real numbers such that the system of linear...

Let α,βand\alpha, \beta and\gammaberealnumberssuchthatthesystemoflinearequations<br>be real numbers such that the system of linear equations<br> \\x+2y+3z=α4x+5y+6z=β7x+8y+9z=γ−1\begin{array}{c}\\ x+2 y+3 z=\alpha\\ \\ 4 x+5 y+6 z=\beta\\ \\ 7 x+8 y+9 z=\gamma-1 \\ \end{array}isconsistent.Let\\ \\ is consistent. Let|M|represent the determinant of the matrix \\ \\ M=\left[α2γβ10−101\begin{array}{ccc}\\ \alpha& 2 & \gamma\\ \\ \beta& 1 & 0 \\ \\ -1 & 0 & 1 \\ \end{array}\right] \\ \\ LetPbetheplanecontainingallthosebe the plane containing all those(\alpha, \beta, \gamma)forwhichtheabovesystemoflinearequationsisconsistent,andfor which the above system of linear equations is consistent, andDbethesquareofthedistanceofthepointbe the square of the distance of the point(0,1,0)fromtheplanefrom the planeP.<br><p>Thevalueof.<br><p>The value ofD$ is

Correct answer

0

Step-by-step solution

x + 2y + 3z = \alpha</p><p></p><p>4x + 5y + 6z = \beta</p><p></p><p>7x + 8y + 9z = \gamma - 1</p><p>Thesystemoflinearequationsisconsistentitmeansithasuniquesolutionorinfinitesolutions</p><p>Here,</p><p>The system of linear equations is consistent it means it has unique solution or infinite solutions</p><p>Here,\Delta = \left|{123456789\begin{cases}1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9\end{cases}\right| = 0</p><p>Hence,thereareinfinitelymanysolutions.</p><p>Ifequationshaveinfinitelymanysolutions,thentheequationsarelinearlyconnected,i.e.,</p><p>Hence, there are infinitely many solutions.</p><p>If equations have infinitely many solutions, then the equations are linearly connected, i.e.,{L}_{1} + \lambda{L}_{2} = {L}_{3}</p><p></p><p>⇒ \left(x + 2y + 3z - \alpha\right) + \lambda ( 4x + 5y + 6z - \beta ) = 7x + 8y + 9z - \gamma + 1</p><p></p><p>\dfrac{1 + 4\lambda}{7} = \dfrac{2 + 5\lambda}{8} = \dfrac{3 + 6\lambda}{9} = \dfrac{\alpha + \lambda\beta}{\gamma - 1}</p><p></p><p>\dfrac{1 + 4\lambda}{7} = \dfrac{2 + 5\lambda}{8} ⇒ \lambda = - 2</p><p>Also,</p><p>Also,\dfrac{1 + 4\lambda}{7} = \dfrac{\alpha + \lambdaB}{\gamma - 1}</p><p></p><p>⇒ - 1 = \dfrac{\alpha - 2\beta}{r - 1}</p><p></p><p>⇒ \alpha - 2\beta + \gamma = 1</p><p>Now,</p><p>Now,Pistheplanecontainingthepoints(α,β,γ)is the plane containing the points \left(\alpha, \beta, \gamma\right)

So, the equation of the plane is x−2y+z=1x - 2y + z = 1 (replacing α,β,γ\alpha, \beta, \gamma by x,y,zx, y, z)

We know, the distance of a point \left({x}_{1}, {y}_{1}, {z}_{1}\right)fromplanefrom planeax + by + cz + d = 0is∣ax1+by1+cz1+da2+b2+c2∣is \left|\dfrac{a{x}_{1} + b{y}_{1} + c{z}_{1} + d}{\sqrt{{a}^{2} + {b}^{2} + {c}^{2}}}\right|

So, D=(0×1−2×1+0×1−112+(−2)2+12)2=96=1.50D = {\left(\dfrac{0 \times 1 - 2 \times 1 + 0 \times 1 - 1}{\sqrt{{1}^{2} + ( - 2{)}^{2} + {1}^{2}}}\right)}^{2} = \dfrac{9}{6} = 1 . 50

Practice Determinants on Quantrex Academy →

More from Determinants

If the system of linear equations: x+y+z=6 , x+2y+5z=10 , 2x+3y+λ z=μ has infinitely many… JEE Main 2026The sum of all possible values of θ ∈ [0, 2π] , for which the system of equations : x 3θ… JEE Main 2026If f: N arrow Z is defined by f(n) = vmatrix n & -1 & -5 -2n^2 & 3(2k+1) & 2k+1 -3n^3 &… JEE Main 2026Consider the system of linear equations in x, y, z : x + 2y + tz = 0 , 6x + y + 5tz = 0… JEE Main 2026If the system of equations: x+y+z=5 x+2y+3z=9 x+3y+λ z=μ has infinitely many solutions… JEE Main 2026If the system of equations x + 5y + 6z = 4 , 2x + 3y + 4z = 7 , x + 6y + az = b has… JEE Main 2026Let α, β ∈ ℝ be such that the system of linear equations x + 2y + z = 5 2x + y + α z = 5… JEE Main 2026The system of linear equations x+y+z=6 2 x+5 y+a z=36 x+2 y+3 z=b has JEE Main 2026Among the statements : I: If | array ccc 1 & α & β α & 1 & γ β & γ & 1 array |=| array… JEE Main 2026Let n be the number obtained on rolling a fair die. If the probability that the system… JEE Main 2026If the system of equations 3 x+y+4 z=3 2 x+α y-z=-3 x+2 y+z=4 has no solution, then the… JEE Main 2026Let the system of equations aligned & x+5 y-z=1 & 4 x+3 y-3 z=7 & 24 x+y+λ z=μ aligned λ… JEE Main 2025Let the system of equations : aligned & 2 x+3 y+5 z=9 & 7 x+3 y-2 z=8 & 12 x+3 y-(4+λ)… JEE Main 2025If y(x)=| array ccc x & x & x+ x+1 27 & 28 & 27 1 & 1 & 1 array |, x ∈ ℝ , then (d^2… JEE Main 2025If the system of equation aligned & 2 x+λ y+3 z=5 & 3 x+2 y-z=7 & 4 x+5 y+μ z=9 aligned… JEE Main 2025If the system of linear equations aligned & 3 x+y+β z=3 & 2 x+α y-z=-3 & x+2 y+z=4… JEE Main 2025 Full Determinants list Determinants JEE Maths PYQsJEE Mathematics PYQs All JEE Advanced PYQs