Concept: The general term of the expansion of (x+a)n is usually denoted by Tr+1=nCrxn−rar
Calculation: For the given expression (3x+2y)15,n=15 (r+1)th term Tr+1=15Cr(3x)15−r(2y)r For the coefficient of x5y10,r must be 10 . T10+1=15C10(3x)15−10(2y)10 T10+1=15C10(3x)5(2y)10 T10+1=15C1035210x5y10 So the coefficient of x5y10 is equal to the 15C1035210