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Find the coefficients of x^7 in (a x^2+1...

Find the coefficients of `x^7` in `(a x^2+1/(b x))^(11)`a n d`x^(-7)in(a x^-1/(b x^2))^(11)` and find the relation between `aa n db` so that coefficients are equal.

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General term `T_(r+1)`​ in the expansion of `(a+b)^n` is given by
`T_(r+1​)=n_(C_r)​a^(n−r)b^r`
Applying to `(ax^2+1/(bx)​)^11,` we get
`T_(r+1)​=11_(C_r)​x^(22−3r)a^11(ab)^(−r) ...(i)`
...
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