Question

Find the tenth term in the expansion of
$\rm \bigg(3a+\frac{4}{a}\bigg)^{13}$

Answer 1

Solution :

$\rm \bigg(3a+\frac{4}{a}\bigg)^{13}$

Compare given binomial with ( X + m )ⁿ,

we get

X = 3a , m = 4/a , n = 13

We know that ,

t( r + 1 ) = ⁿCr ( x )^n-r m^r

Now ,

t10 = t (9 + 1)

= 13C9 ( 3a )^13-9 ( 4/a )^9

= 13C9 ( 3a )⁴ ( 4/a )^9

= 13C9 (3⁴ × 4^9) a⁴/a^9

= 13C9 ( 3⁴ × 4^9 ) ( 1/a^5 )

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