For what values of 'a' does the equation ax^2 - (a + 1)x + 3 = 0, have roots lying between 1 and 2?
The quadratic formula states for a quadratic equation , the solution is
In your case, , so your solutions are
The small root is
while the larger root is
Your constraint say that and , so find the values of such that those two inequalities are satisfied.
Can you take it from there?