Question

The constant term in the expansion of $\left(2 x+\frac{1}{x^7}+3 x^2\right)^5$ is_____

Answer 1

The correct answer is 1080.
General term is ∑n1​!n2​!n3​!5!(2x)n1​(x−7)n2​(3x2)n3​​
For constant term,
n1​+2n3​=7n2​
&n1​+n2​+n3​=5
Only possibility n1​=1,n2​=1,n3​=3
⇒ constant term =1080