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ExamsJEE MainMaths

The equation (2 + log₁₀(x))³ + (log₁₀(x) - 1)³ = (1 + log₁₀(x²))³ has how many solutions, and of what type?

  1. Two irrational and one rational solutions
  2. One irrational and two rational solutions
  3. One irrational and two prime number solutions
  4. All rational solutions

Correct answer: Two irrational and one rational solutions

Solution

Let a=2+t, b=t-1, c=1+2t=a+b. Equation becomes a³+b³=c³=(a+b)³. So 3ab(a+b)=0 => ab=0 or a+b=0. ab=0: (2+t)(t-1)=0 => t=-2 or t=1 => x=0.01 or x=10 (both rational). a+b=0: 2t+1=0 => t=-1/2 => x=10^(-1/2)=1/sqrt(10) (irrational). So three solutions: two rational (x=1/100 and x=10) and one irrational (x=1/sqrt(10)). Wait — 'two rational and one irrational' matches option B. But option A says 'two irrational and one rational'. Recheck: t=-2 -> x=10^(-2)=0.01 (rational), t=1 -> x=10 (rational), t=-1/2 -> x=10^(-1/2) (irrational). So: 1 irrational + 2 rational. Answer is option B.

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