Q34 / 90 · JEE Main 2021 (18 Mar Shift 2) · Mathematics

Let f:R-{3}→R-{1} be defined by fx=x-2x-3. Let g : R→R be given as g(x)=2x-3. Then, the sum of all the values of x for which f-1x+g-1x=132 is equal to

  • A
    7
  • B
    2
  • Correct answer
    C
    5
  • D
    3

Solution

fx=y=x-2x-3

∴x=3y-2y-1

∴f-1x=3x-2x-1

& g(x)=y=2 x-3

∴x=y+32

∴g-1x=x+32

∵f-1x+g-1x=132

3x-2x-1+x+32=132

∴ x2-5x+6=0 has roots x1,x2

∴ sum of roots x1+x2=5

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

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