Find the coefficient of the x^9 in the expansion of (3x^4 − 1/x)^6

By the binomial theorem:

where

is the binomial coefficient. Now,

and the x⁹ term occurs when 24 - 5k = 9, or k = 3, so the coefficient is

.

step-by-step explanation:

.

2.2°  

step-by-step explanation:

let θ = the angle of elevation.

tanθ =77/2020

tanθ = 0.038 12

      θ = tan⁻¹0.038 12

      θ = 2.2°