Q73 / 125 · BITSAT 2019 · Mathematics

Let a,b,c∈R+ and the system of equations (1-a)x+y+z=0,x+(1-b)y+z=0 and x+y+(1-c)z=0 has infinitely many solutions, the minimum value of abc is

  • A
    33
  • B
    9
  • Correct answer
    C
    27
  • D
    3

Solution

We have,

1-ax+y+z=0

x+1-by+z=0

x+y+1-cz=0

has many solutions 

∴ 1-a1111-b1111-c=0

⇒ ab+ac+bc=abc

∴ ab+bc+ac3≥a2b2c21/3⇒abc1/3≥3

∴ Minimum of abc=33=27

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

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