NIMCET 2009 — Mathematics PYQ
NIMCET | Mathematics | 2009If and , then is equal to:

If P={(4n−3n−1)∣n∈N} and Q={(9n−9)∣n∈N}, then P∪Q is equal to:
N
P
Q
(Correct Answer)None
Q
To solve this, let's analyze the elements of sets P and Q by substituting values of n (where n=1,2,3,…).
1. Analyzing Set P
The general term for set P is 4n−3n−1.
For n=1: 41−3(1)−1=4−3−1=0
For n=2: 42−3(2)−1=16−6−1=9
For n=3: 43−3(3)−1=64−9−1=54
For n=4: 44−3(4)−1=256−12−1=243
So, P={0,9,54,243,…}
2. Analyzing Set Q
The general term for set Q is 9n−9, which can be written as 9(n−1).
For n=1: 9(1−1)=0
For n=2: 9(2−1)=9
For n=3: 9(3−1)=18
For n=4: 9(4−1)=27
For n=5: 9(5−1)=36
...
For n=7: 9(7−1)=54
So, Q={0,9,18,27,36,45,54,…}
3. Comparison and Conclusion
From the values calculated:
Set Q consists of all non-negative multiples of 9.
Set P consists of some specific multiples of 9 (using binomial expansion, 4n=(1+3)n=1+3n+2n(n−1)32+…, so 4n−3n−1 is always divisible by 9).
Every element in P is also found in Q, but Q contains many elements (like 18,27,36) that are not in P.
Therefore, P⊂Q (P is a subset of Q).
When one set is a subset of another, their union is the larger set:
Final Answer:
The correct option is (c) Q.
To solve this, let's analyze the elements of sets P and Q by substituting values of n (where n=1,2,3,…).
1. Analyzing Set P
The general term for set P is 4n−3n−1.
For n=1: 41−3(1)−1=4−3−1=0
For n=2: 42−3(2)−1=16−6−1=9
For n=3: 43−3(3)−1=64−9−1=54
For n=4: 44−3(4)−1=256−12−1=243
So, P={0,9,54,243,…}
2. Analyzing Set Q
The general term for set Q is 9n−9, which can be written as 9(n−1).
For n=1: 9(1−1)=0
For n=2: 9(2−1)=9
For n=3: 9(3−1)=18
For n=4: 9(4−1)=27
For n=5: 9(5−1)=36
...
For n=7: 9(7−1)=54
So, Q={0,9,18,27,36,45,54,…}
3. Comparison and Conclusion
From the values calculated:
Set Q consists of all non-negative multiples of 9.
Set P consists of some specific multiples of 9 (using binomial expansion, 4n=(1+3)n=1+3n+2n(n−1)32+…, so 4n−3n−1 is always divisible by 9).
Every element in P is also found in Q, but Q contains many elements (like 18,27,36) that are not in P.
Therefore, P⊂Q (P is a subset of Q).
When one set is a subset of another, their union is the larger set:
Final Answer:
The correct option is (c) Q.