Number of Real Roots in Logarithmic Equation
XAT 2025 · Quantitative Ability & Data Interpretation · Hard · Logarithms
For how many distinct real values of does the equation below hold true? (Consider .)
- A.
1
- B.
Infinitely many
- C.
2
- D.
0
- E.
Depends on the value of a
Answer
E
Explanation
Simplify the ratios using base change rule :
- .
- . The equation becomes: . So or . However, for terms to be defined, base must satisfy and . If , the terms are undefined. Thus the valid roots depend on whether is valid (). Therefore, the answer depends on the value of .
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