What is the 9th term of #(2x+y)^12 ?#

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Answer 1 · 2018-06-15T09:46:57

# 7920x^4y^8#.

We know that, the #(r+1)^(th)# term , i.e., #T_(r+1)# in the

expansion of #(a+b)^n# is given by,

#T_(r+1)=""_nC_ra^(n-r)b^r, r=0,1,2,...,n.#

In our Problem, #a=2x, b=y, n=12, r+1=9, or, r=8#.

#:. T_9=""_12C_8(2x)^(12-8)(y)^8=""_12C_4(2x)^4y^8#,

#={(12)(11)(10)(9)}/{(1)(2)(3)(4)}16x^4y^8#.

# rArr T_9=7920x^4y^8#.