Standard +0.8 This requires expanding two binomial expressions, collecting terms systematically, and proving a specific coefficient vanishes through algebraic manipulation. It demands careful organization and algebraic insight beyond routine expansion, but uses only standard binomial theorem techniques.
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.
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.\\
\hfill \mbox{\textit{CAIE P1 Q1 [3]}}