Question
Question: The coefficient of \(x^{5}\) in the expansion of \((1 + x^{2})^{5}(1 + x)^{4}\) is...
The coefficient of x5 in the expansion of (1+x2)5(1+x)4 is
A
30
B
60
C
40
D
None of these
Answer
60
Explanation
Solution
We have (1+x2)5(1+x)4 = (5⥂C0+5⥂C1x2+5⥂C2x4+.....)
(4⥂C0+4⥂C1x1+4⥂C2x2+.......)
So coefficient of x5 in [(1+x2)5(1+x)4]
= 5C2.4C1+4⥂C3.5C1=60