The quadratic equation X2 + X+ K =0 has roots a and b Use the substitution x 2u+ 1 to obtain a quadratic equation in u. \begin{aligned} &\left(\frac{\alpha-1}{2}\right)\left(\frac{\beta-1}{2}\right) \text {

in terms of } k\\ &\text { Hence, or otherwise, find the value of } \end{aligned}