Given that kkk is a constant and the binomial expansion of 1+kx,∣kx∣<1\sqrt{1 + kx}, \quad |kx| < 11+kx,∣kx∣<1 in ascending powers of xxx up to the term in x3x^3x3 is 1+14x+Ax2+Bx31 + \frac{1}{4}x + Ax^2 + Bx^31+41x+Ax2+Bx3
(i) find the value of kkk,
(ii) find the value of the constant AAA and the constant BBB.
Use the expansion to find an approximate value to 1.2\sqrt{1.2}1.2.
Show your working and give your answer to 6 decimal places.