Question 4
A4 (BUL 2). Determine all real values of the parameter $a$ for which the equation
$$16x^4-ax^3+(2a+17)x^2-ax+16=0$$
has exactly four distinct real roots that form a geometric progression.
$$16x^4-ax^3+(2a+17)x^2-ax+16=0$$
has exactly four distinct real roots that form a geometric progression.