JEE Advanced | 2014Math miscellaneousHard
Question
Coefficient of x11 in the expansion of (1 + x2)4(1 + x3)7(1 + x4)12 is
Options
A.1051
B.1106
C.1113
D.1120
Solution
Power of Coefficient of x11
x2 x3 x4 4C0 × 7C1 × 12C2
0 1 2 4C2 × 7C1 × 12C1
2 1 1 4C4 × 7C1 × 12C0
4 1 0 4C1 × 7C3 × 12C0
1 3 0
1113

x2 x3 x4 4C0 × 7C1 × 12C2
0 1 2 4C2 × 7C1 × 12C1
2 1 1 4C4 × 7C1 × 12C0
4 1 0 4C1 × 7C3 × 12C0
1 3 0

1113

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