Q33 / 90 · JEE Main 2022 (24 Jun Shift 2) · Mathematics

Let the system of linear equations
x+y+az=2

3x+y+z=4

x+2z=1
have a unique solution x,y,z. If α,x,y,α and x,-y are collinear points, then the sum of absolute values of all possible values of α is

  • A
    4
  • B
    3
  • Correct answer
    C
    2
  • D
    1

Solution

Given,
x+y+az=2

3x+y+z=4

x+2z=1
Now finding,

Δ=11α311102=-α+3

Δ1=21α411102=-3+α

Δ2=12α341112=-α+3

Δ3=112314101=0

α≠-3,x=△1△=1,y=△2△=1,z=△3△=0,

Now points α,1,1,α & 1,-1 are collinear

α111α11-11=0

⇒αα+1-11-1+1-1-α=0

α2+α-1-α=0

α=±1

So, 1+-1=2

Hence, the correct answer is option: 'C'.

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