It is given that x=2,y=3 By the expansion of (2x−3y)8 middle term is 5th term. a=8C4(2x)4(3y)4(−1)4 a=
8!
4!4!
×24×34×x2y2 =70×24×34×24×34 Similarly, in the expansion of (3x+4y)7,4 th and 5 th terms are middle terms. b=7C3(3x)4(4y)3 =35×37×210 c=7C4(3x)3(4y)4 =35×37×211 Now