someone pls help me with this

Plz i want answer and i would appreciate it is is a b c or d

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

50 plz, given the system of equations, match the following items. x + 3 y = 5 x - 3 y = -1 a) x-determinant b) y-determinant c) system determinant match the following to the pictures below.