2a^2-3a-2/4a^2-1 (4a^2-1 = denominator) divided by a^2-4/2a^2-5a+2 <--- denominator
(2a^2-3a-2)/(4a^2-1) Divided by
(a^2-4)/(2a^2-5a+2)
Invert divisor(2nd fraction) and multiply:
(2a^2-3a-2)/(4a^2-1)*(2a^2-5a+2)/a^2-4.
(a-2)(2a+1)/(2a+1)(2a-1)*(a-2)(2a-1)/
(a+2)(a-2) = (a-2)/(a+2).