Question

(r-8)^5

find the coefficient of the given term
r^3

98 points max

Answer 1

Explanation:

Apply binomial theorem to expand (a+b)^n where a = r, b = -8 n n = 5

the r^3 term is (5!/(2!*(5-2)!)*r^3*(-8)^(5-3)

=(5*4*3*2*1/1*2*1*2*3)*r^3*(-8)^2

=640*r^3

So the coefficient is 640.

Answer 2

640

Explanation:

Expanding the binomial :

r⁵ - 40r⁴ + 640r³ - 5120r² + 20480r - 32768

The coefficient of r³ is 640