Question

What is the coefficient of x^2y^3 in the expansion of (2x+y)^5?

A. 2
B. 5
C. 40
D. 80
E. It does not exist

Answer 1

try the 4 th terms
= 5C3 (2x)^(5-30 y^3

Answer 2

* that is 5C3 (2x)^(5-3) y^3

Answer 3

= 5C3 4x^2 y^3

now you need to calculate 5C3 * 4

Answer 4

the number of combinations of 3 in 5

nCr = n!
-----
(n-r)! r!

Answer 5

so its letter B?

Answer 6

No 5C3 = (5*4*3*2*1
---------
2*1 * 3*2*1

Answer 7

and you need to multiply that by 4