The sum of all the real solutions of the equation
is equal to
- A
- B
- C
- D
The sum of all the real solutions of the equation
is equal to
Correct answer:B
Standard Method
Given:
Find: The sum of all real solutions.
Factor the polynomial terms:
and
Substitute into the equation:
Using logarithmic properties:
Let
Then
using
So the equation becomes
Multiplying by :
Hence,
Therefore,
which gives
So,
Check validity:
Thus the sum of solutions is
Therefore, the correct option is B.
Use reciprocal-log substitution
Given:
Find: The sum of all real solutions.
After factoring,
so the equation reduces to expressions involving
and its reciprocal. This works because
Let
Then the equation directly becomes
which gives
Hence,
Now use the meaning of the logarithm:
So,
and the real solutions are and . Their sum is . Therefore, the correct option is B.
A common mistake is to miss the factorization and . Without this simplification, the log expressions do not reduce neatly. Always factor first before applying logarithmic properties.
Students often forget the reciprocal identity and incorrectly treat as equal to . They are reciprocals, not equal in general.
Another mistake is to solve for from and stop there without checking the logarithm domain. For logarithms, the bases must be positive and not equal to , and the arguments must be positive. Always verify each obtained root in the original equation.
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