Coefficient zero by design (proof)

Questions that ask to prove or show that a specific coefficient is zero for a given expression with parameters, rather than finding the parameter value.

2 questions

CAIE P1 2015 November Q1

1 In the expansion of \(\left( 1 - \frac { 2 x } { a } \right) ( a + x ) ^ { 5 }\), where \(a\) is a non-zero constant, show that the coefficient of \(x ^ { 2 }\) is zero.

CAIE P1 Specimen Q1

1 In the expansion of \(\left( 1 - \frac { 2 x } { a } \right) ( a + x ) ^ { 5 }\), where \(a\) is a non-zero constant, show that the coefficient of \(x ^ { 2 }\) is zero.