For this case we have the following polynomial:
[tex]3x ^ 2 + 9x + 15[/tex]
The standard form of the polynomial is given by:
[tex]ax ^ 2 + bx + c[/tex]
Where, the axis of symmetry of the polynomial is given by the expression:
[tex]x = - \frac {b} {2a}[/tex]}
In this case we have:
[tex]a = 3\\b = 9[/tex]
Therefore, replacing values we have:
[tex]x = - \frac {9} {2 (3)}[/tex]
Rewriting we have:
[tex]x = - \frac {9} {6}\\x = - \frac {3} {2}[/tex]
Answer:
The symmetry axis of the polynomial is given by:
[tex]x = - \frac {3} {2}[/tex]
option C
