If the system of linear equations x + y + 3 z = 0 x + 3 y + k 2 z = 0 3 x + y + 3 z = 0 has a non-zero…

If the system of linear equations
x+y+3z=0
x+3y+k2z=0
3x+y+3z=0
has a non-zero solution (x, y, z) for some kR, then x+yz is equal to :
  1. -3
  2. 9
  3. 3
  4. -9

Solution

So D=011313k2313=0    k2=9

x+y+3 z=0

x+3 y+9 z=0

3 x+y+3 z=0

(1)-(3)
x=0  y+3z=0

yz=-3
so, x+yz=-3

 

Asked in: JEE Main 2020 (05 Sep Shift 2)

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