Expand \(( 1 + y ) ^ { 6 }\) in ascending powers of \(y\) as far as the term in \(y ^ { 2 }\).
In the expansion of \(\left( 1 + \left( p x - 2 x ^ { 2 } \right) \right) ^ { 6 }\) the coefficient of \(x ^ { 2 }\) is 48 . Find the value of the positive constant \(p\).