Answer:
The axis of symmetry is
[tex]x=-\frac{3}{2}[/tex]
Step-by-step explanation:
The given function is [tex]f(x)=3x^2+9x+15[/tex].
Compare to [tex]f(x)=ax^2+bx+c[/tex],
[tex]a=3,b=9,c=15[/tex]
The axis of symmetry of the parabola is given by the formula;
[tex]x=-\frac{b}{2a}[/tex]
We substitute into the formula to get;
[tex]x=-\frac{9}{2(3)}[/tex]
The axis of symmetry is
[tex]x=-\frac{3}{2}[/tex]