(i) Given that \(a\) is a constant, expand \((2+ax)^4\), in ascending powers of \(x\), simplifying each term of your expansion.

Given also that the coefficient of \(x^2\) is equal to the coefficient of \(x^3\),

(ii) show that \(a=3\),

(iii) use your expansion to show that the value of \(1.97^4\) is \(15.1\) to 1 decimal place.