Q31 / 90 · JEE Main 2017 (02 Apr) · Mathematics

If S is the set of distinct values of b for which the following system of linear equations

x+y+z=1

x+ay+z=1

ax+by+z=0

has no solution, then S  is:

  • A
    An empty set
  • B
    An infinite set
  • C
    A finite set containing two or more elements
  • Correct answer
    D
    A singleton

Solution

For no solution D=1111a1ab1=0

Expanding the determinant along the first row, we get D=-a-12=0

⇒   a=1

For a=1, first two planes are coincident.

Now, we have x+y+z=1 & ax+by+z=0

For no solution, these two planes are parallel.

⇒1a=1b=11

⇒a=1 & b=1.

∴   b=1 ⇒ it is a singleton set

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

Relevant Questions