1. The total number of terms in the expansion of (x + a)ⁿ is:
A. n + 1
B. n
C. n - 1
D. 2ⁿ
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Answer: A. n + 1
Explanation: The binomial expansion of (x + a)ⁿ contains exactly (n + 1) terms.
2. The general term (r + 1)th term Tᵣ₊₁ in the expansion of (a + b)ⁿ is:
A. ⁿCᵣ aⁿ⁻ʳ bʳ
B. ⁿCᵣ aʳ bⁿ⁻ʳ
C. ⁿCᵣ⁻₁ aⁿ⁻ʳ bʳ
D. ⁿCᵣ₊₁ aⁿ⁻ʳ bʳ
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Answer: A. ⁿCᵣ aⁿ⁻ʳ bʳ
Explanation: By definition, the (r + 1)th term is Tᵣ₊₁ = ⁿCᵣ aⁿ⁻ʳ bʳ.
3. The sum of all binomial coefficients in the expansion of (1 + x)ⁿ is:
A. 2ⁿ
B. 2ⁿ⁻¹
C. 2ⁿ⁺¹
D. n²
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Answer: A. 2ⁿ
Explanation: Substituting x = 1 in (1 + x)ⁿ = ⁿC₀ + ⁿC₁x + ... + ⁿCₙxⁿ gives 2ⁿ = ⁿC₀ + ⁿC₁ + ... + ⁿCₙ.
4. The sum of coefficients of even terms ⁿC₀ + ⁿC₂ + ⁿC₄ + ... is equal to:
A. 2ⁿ⁻¹
B. 2ⁿ
C. 2ⁿ⁺¹
D. 2ⁿ - 1
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Answer: A. 2ⁿ⁻¹
Explanation: The sum of even-indexed coefficients equals the sum of odd-indexed coefficients, each equal to 2ⁿ / 2 = 2ⁿ⁻¹.
5. Number of terms in the expansion of (x + 2y)⁹ is:
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Answer: A. 10
Explanation: Number of terms = n + 1 = 9 + 1 = 10.
6. If n is even, the middle term in the expansion of (a + b)ⁿ is:
A. (n/2 + 1)th term
B. (n/2)th term
C. ((n+1)/2)th term
D. (n/2 + 2)th term
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Answer: A. (n/2 + 1)th term
Explanation: When n is even, there is only one middle term, which is the (n/2 + 1)th term.
7. If n is odd, the middle terms in the expansion of (a + b)ⁿ are:
A. ((n+1)/2)th and ((n+3)/2)th terms
B. (n/2)th and (n/2 + 1)th terms
C. (n+1)th and (n+2)th terms
D. ((n-1)/2)th and ((n+1)/2)th terms
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Answer: A. ((n+1)/2)th and ((n+3)/2)th terms
Explanation: When n is odd, there are two middle terms: the ((n+1)/2)th and ((n+3)/2)th terms.
8. The 4th term in the expansion of (x - 2y)¹² is:
A. -1760 x⁹ y³
B. 1760 x⁹ y³
C. -220 x⁹ y³
D. -1760 x⁸ y⁴
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Answer: A. -1760 x⁹ y³
Explanation: T₄ = ¹²C₃ x⁹ (-2y)³ = 220 × x⁹ × (-8y³) = -1760 x⁹ y³.
9. The coefficient of x⁵ in the expansion of (x + 3)⁸ is:
A. 1512
B. 56
C. 27
D. 1120
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Answer: A. 1512
Explanation: Term with x⁵ is T₄ = ⁸C₃ x⁸⁻³ 3³ = 56 × x⁵ × 27 = 1512 x⁵. Coefficient is 1512.
10. Find the middle term in the expansion of (x + 1/x)¹⁰:
A. 252
B. 210
C. 120
D. 252 x
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Answer: A. 252
Explanation: n = 10 (even). Middle term = (10/2 + 1) = 6th term. T₆ = ¹⁰C₅ x⁵ (1/x)⁵ = 252.
11. The term independent of x in the expansion of (x + 1/x)²ⁿ is:
A. ²ⁿCₙ
B. ²ⁿCₙ₊₁
C. ²ⁿCₙ⁻¹
D. ⁿCₙ
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Answer: A. ²ⁿCₙ
Explanation: Tᵣ₊₁ = ²ⁿCᵣ x²ⁿ⁻ʳ (1/x)ʳ = ²ⁿCᵣ x²ⁿ⁻²ʳ. For term independent of x, 2n - 2r = 0 ⇒ r = n. So term is ²ⁿCₙ.
12. What is the value of ⁿC₀ - ⁿC₁ + ⁿC₂ - ⁿC₃ + ... + (-1)ⁿ ⁿCₙ?
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Answer: A. 0
Explanation: Put x = -1 in (1 + x)ⁿ = (1 - 1)ⁿ = 0ⁿ = 0.
13. In the expansion of (a - b)ⁿ, the signs of the terms are:
A. Alternately positive and negative
B. All positive
C. All negative
D. Dependent on n only
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Answer: A. Alternately positive and negative
Explanation: Due to (-b)ʳ, odd powers of b introduce negative signs, resulting in alternating signs.
14. Number of terms in the expansion of (x + a)ⁿ + (x - a)ⁿ when n is even is:
A. n/2 + 1
B. n/2
C. (n + 1)/2
D. n + 1
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Answer: A. n/2 + 1
Explanation: Odd terms cancel out, leaving (n/2 + 1) even-indexed non-zero terms.
15. Number of terms in the expansion of (x + a)ⁿ - (x - a)ⁿ when n is even is:
A. n/2
B. n/2 + 1
C. (n + 1)/2
D. n
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Answer: A. n/2
Explanation: Even terms cancel out, leaving exactly n/2 terms.
16. The coefficient of a²b³ in the expansion of (a + b)⁵ is:
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Answer: A. 10
Explanation: Coefficient is ⁵C₃ = (5 × 4 × 3) / (3 × 2 × 1) = 10.
17. Find the coefficient of x⁶ y³ in the expansion of (x + 2y)⁹:
A. 672
B. 84
C. 504
D. 252
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Answer: A. 672
Explanation: T₄ = ⁹C₃ x⁶ (2y)³ = 84 × x⁶ × 8y³ = 672 x⁶ y³. Coefficient is 672.
18. The number of terms in the expansion of (a + b + c)ⁿ is:
A. (n + 1)(n + 2) / 2
B. n + 1
C. n + 2
D. (n + 1)²
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Answer: A. (n + 1)(n + 2) / 2
Explanation: For a trinomial expansion, total number of terms is ⁿ⁺²C₂ = (n + 1)(n + 2) / 2.
19. The number of terms in (x + y + z)¹⁰ is:
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Answer: A. 66
Explanation: Formula: (10 + 1)(10 + 2) / 2 = (11 × 12) / 2 = 66.
20. The 13th term in the expansion of (9x - 1/(3√x))¹⁸ is:
A. 18564
B. 18564 x
C. 18564 / x
D. 18564 x²
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Answer: A. 18564
Explanation: T₁₃ = ¹⁸C₁₂ (9x)⁶ (-1 / (3√x))¹² = 18564 × (9⁶ x⁶) × (1 / (3¹² x⁶)) = 18564 (since 9⁶ = 3¹²).
21. Expanding (101)⁴ using Binomial Theorem gives:
A. 104060401
B. 104060400
C. 104040601
D. 104060101
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Answer: A. 104060401
Explanation: (100 + 1)⁴ = 100⁴ + 4(100³) + 6(100²) + 4(100) + 1 = 100000000 + 4000000 + 60000 + 400 + 1 = 104060401.
22. Which is larger: (1.1)¹⁰⁰⁰⁰ or 1000?
A. (1.1)¹⁰⁰⁰⁰
B. 1000
C. Both are equal
D. Cannot be determined
Show Answer
Answer: A. (1.1)¹⁰⁰⁰⁰
Explanation: (1 + 0.1)¹⁰⁰⁰⁰ = 1 + 10000(0.1) + ... = 1 + 1000 + positive terms > 1000.
23. In Pascal's Triangle, each row starts and ends with:
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Answer: A. 1
Explanation: Every row in Pascal's Triangle begins with ⁿC₀ = 1 and ends with ⁿCₙ = 1.
24. The middle term in the expansion of (x/3 + 9y)¹⁰ is:
A. 61236 x⁵ y⁵
B. 252 x⁵ y⁵
C. 61236 x⁶ y⁴
D. 61236 x⁴ y⁶
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Answer: A. 61236 x⁵ y⁵
Explanation: Middle term is T₆ = ¹⁰C₅ (x/3)⁵ (9y)⁵ = 252 × (x⁵ / 243) × 59049 y⁵ = 61236 x⁵ y⁵.
25. In the binomial expansion of (a + b)ⁿ, the degree of each term is always:
A. n
B. n - 1
C. n + 1
D. Variable
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Answer: A. n
Explanation: In every term ⁿCᵣ aⁿ⁻ʳ bʳ, the sum of indices is (n - r) + r = n.
26. If the coefficient of x⁷ and x⁸ are equal in (2 + x/3)ⁿ, then n is:
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Answer: A. 55
Explanation: Equating coefficients: ⁿC₇ 2ⁿ⁻⁷ (1/3)⁷ = ⁿC₈ 2ⁿ⁻⁸ (1/3)⁸ ⇒ ⁿC₇ × 2 = ⁿC₈ × (1/3) ⇒ 6 = ⁿC₈ / ⁿC₇ = (n - 7) / 8 ⇒ n - 7 = 48 ⇒ n = 55.
27. The first term in the binomial expansion of (x + a)ⁿ is:
A. xⁿ
B. aⁿ
C. n xⁿ⁻¹
D. ⁿC₁ xⁿ
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Answer: A. xⁿ
Explanation: T₁ = ⁿC₀ xⁿ a⁰ = 1 × xⁿ × 1 = xⁿ.
28. The last term in the binomial expansion of (x + a)ⁿ is:
A. aⁿ
B. xⁿ
C. n aⁿ⁻¹
D. ⁿC₁ aⁿ
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Answer: A. aⁿ
Explanation: Tₙ₊₁ = ⁿCₙ x⁰ aⁿ = 1 × 1 × aⁿ = aⁿ.
29. The coefficient of xⁿ⁻¹ in the expansion of (x - 1)(x - 2)(x - 3)...(x - n) is:
A. -n(n + 1) / 2
B. n(n + 1) / 2
C. -n
D. (-1)ⁿ n!
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Answer: A. -n(n + 1) / 2
Explanation: Sum of roots with negative sign = -(1 + 2 + 3 + ... + n) = -n(n + 1)/2.
30. Find the coefficient of x⁴ in the expansion of (1 + x)⁸:
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Answer: A. 70
Explanation: Coefficient is ⁸C₄ = (8 × 7 × 6 × 5) / (4 × 3 × 2 × 1) = 70.