Let S , be the set of all real roots of the equation, 3 x 3 x - 1 + 2 = 3 x - 1 + 3 x - 2 , then

Let S, be the set of all real roots of the equation, 3x3x-1+2=3x-1+3x-2, then
  1. contains exactly two elements.
  2. is a singleton.
  3. is an empty set.
  4. contains at least four elements.

Solution

$3^x = t$ $t|t-1| + 2 = |t-1| + |t-2|$ $t^2 - t + 2 = |t-1| + |t-2|$ Let, $f(t) = t^2 - t + 2$ and $g(t) = |t-1| + |t-2|$ $f(t)$ and $g(t)$ has a solution at $t=a$ $3^x = a \Rightarrow x = \log_3 a$ So, it is a singleton set.

Asked in: JEE Main 2020 (08 Jan Shift 2)

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