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WAEC SSCE - Further Mathematics - 2022 (Objective)

Question 1 Report

Find the coefficient of \(x^3y^2\) in the binomial expansion of \((x-2y)^5\)

Answer Details

x3
y2
 in (x-2y)5


n = 5, r = 3, p = x, q = -2y

 

5C3 3  * x3
 -2y
2

5C3 3  = 5![5−3]!3!

5∗4∗3!2!3!
 →  5∗42

5C3
 = 10

: 5C3
 * x3
 -2y2
 = 10 *  x3
 4y2

 40x3
y2

the coefficient is 40