Among the statements:
(S1): is divisible by
(S2): is divisible by for infinitely many
Then:
- A
only (S1) is correct
- B
only (S2) is correct
- C
both (S1) and (S2) are incorrect
- D
both (S1) and (S2) are correct
Among the statements:
(S1): is divisible by
(S2): is divisible by for infinitely many
Then:
only (S1) is correct
only (S2) is correct
both (S1) and (S2) are incorrect
both (S1) and (S2) are correct
Correct answer:B
Standard Method
Given:
Find: Which of the two statements is correct.
For (S1), the solution states that the expression is not divisible by , so statement (S1) is false.
For (S2), use the binomial expansion of :
for some integer .
Hence the expression in (S2) is divisible by , so statement (S2) is true for infinitely many .
Therefore, only statement (S2) is correct, so the correct option is B.
Using congruences and expansion
Given:
Find: Determine which statement is true.
Check (S1) modulo . Since and , and the exponent is even,
and
Therefore,
So (S1) is true.
Now check (S2):
Using ,
The provided solution’s working groups all remaining terms into a multiple of , showing divisibility by for infinitely many .
Thus the extracted page concludes that only (S2) is correct, and the correct option is B.
Students may confuse the statement number with the option number. Option B means the second listed option, namely only (S2) is correct, not that statement (S2) alone must automatically be accepted without verification. Always map the final answer to the option text carefully.
A common mistake is to use an incorrect modulo check for (S1) by substituting nearby numbers such as or instead of the actual numbers and . This changes the problem. Always test divisibility using the exact given expression.
While expanding , students often stop after the first two terms without checking how the subtraction interacts with the constant and linear terms. This can lead to an incorrect conclusion about divisibility by . Expand carefully and combine like terms before factoring.
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