Question 1 - A-Level Maths

Exam Board	CAIE
Module	P1 (Pure Mathematics 1)
Year	2020
Session	November
Topic	Binomial Theorem (positive integer n)
Type	Product with unknown constant to determine

1 The coefficient of \(x ^ { 3 }\) in the expansion of \(( 1 + k x ) ( 1 - 2 x ) ^ { 5 }\) is 20 .
Find the value of the constant \(k\).