Application Of Derivatives

Let 'a' be a real number such that the function f(x) = ax² + 6x \(-\) 15, x \(\in\) R is increasing in \(\left( { - \infty ,{3 \over 4}} \right)\) and decreasing in \(\left( {{3 \over 4},\infty } \right)\). Then the function g(x) = ax² \(-\) 6x + 15, x\(\in\)R has a :