Related Formula
General term of binomial expansion (x + y)ⁿ$(x + y)^n$:
Tk+1 = nk xn-k y^k$$T_{k+1} = \binom{n}{k} x^{n-k} y^k$$
Condition for three terms A, B, C$A, B, C$ to be in G.P.:
B² = A · C$B^2 = A \cdot C$
Core Logic
Part 1: Coefficients of Tᵣ, Tᵣ₊₁, Tᵣ₊₂$T_r, T_{r+1}, T_{r+2}$ are 12r-1, 12r, 12r+1$\binom{12}{r-1}, \binom{12}{r}, \binom{12}{r+1}$.
Since they are in G.P.:
[ 12r]² = 12r-1 · 12r+1$$\left[\binom{12}{r}\right]^2 = \binom{12}{r-1} \cdot \binom{12}{r+1}$$
12r 12r-1 = 12r+1 12r (12-r+1)/(r) = (12-r)/(r+1)$$\frac{\binom{12}{r}}{\binom{12}{r-1}} = \frac{\binom{12}{r+1}}{\binom{12}{r}} \implies \frac{12-r+1}{r} = \frac{12-r}{r+1}$$
(13-r)(r+1) = r(12-r) 13r + 13 - r² - r = 12r - r²$$(13-r)(r+1) = r(12-r) \implies 13r + 13 - r^2 - r = 12r - r^2$$
12r + 13 = 12r 13 = 0 (Not possible)$$12r + 13 = 12r \implies 13 = 0 \quad (\text{Not possible})$$
Thus, no real integer solution for r$r$ exists, so p = 0$p = 0$.
Step 1: Calculate Rational Terms Sum q
Part 2: Rational terms in expansion of (31/4 + 41/3)¹²$(3^{1/4} + 4^{1/3})^{12}$.
General term:
Tk+1 = 12k (31/4)12-k (41/3)^k = 12k 3(12-k)/(4) 4(k)/(3)$$T_{k+1} = \binom{12}{k} (3^{1/4})^{12-k} (4^{1/3})^k = \binom{12}{k} 3^{\frac{12-k}{4}} 4^{\frac{k}{3}}$$
For the term to be rational, (12-k)/(4)$\frac{12-k}{4}$ and \frac{k}{3} must both be integers:
T₁ = 120 3³ 4⁰ = 1 × 27 × 1 = 27$$T_1 = \binom{12}{0} 3^3 4^0 = 1 \times 27 \times 1 = 27$$
T₁₃ = 1212 3⁰ 4⁴ = 1 × 1 × 256 = 256$$T_{13} = \binom{12}{12} 3^0 4^4 = 1 \times 1 \times 256 = 256$$
Sum of rational terms q = 27 + 256 = 283$q = 27 + 256 = 283$.
Step 2: Final Combination
p + q = 0 + 283 = 283$$p + q = 0 + 283 = 283$$
Pattern Recognition
To find common values for divisibility constraints, look for multiples of the least common multiple (3, 4) = 12$\text{\lcm}(3, 4) = 12$ within the range [0, 12]$[0, 12]$.
Chapter Mix
Class 11 Mathematics: Binomial Theorem