can someone explain how to find the answer please?

What is the axis of symmetry for f(x) = −3x2 + 18x − 7?

x = −3

x = 3

x = −6

x = 6

Question

can someone explain how to find the answer please? 

What is the axis of symmetry for f(x) = −3x2 + 18x − 7? 

 x = −3

x = 3

x = −6

x = 6

anonymous · Answer

find the vertex of $f(x) = −3x^2 + 18x − 7 $ or just compute $-\frac{b}{2a}$ with $a=-3,b=18$

anonymous · Answer

axis of symmetry for 
$$y=ax^2+bx+c$$ is 
$$x=-\frac{b}{2a}$$

anonymous · Answer

so all i do is plug in the points, (-3,18), and solve?

anonymous · Answer

not sure what you mean, it is not a point, it is a number

anonymous · Answer

i.e. $$-\frac{b}{2a}=-\frac{18}{2\times (-3)}$$ is what you need to compute for the axis of symmetry

anonymous · Answer

the axis of symmetry is a vertical line
the equation for a vertical line looks like $x=number$
in your case the number is $3$ so the axis of symmetry is $x=3$

anonymous · Answer

okay thank you so much!

anonymous · Answer

yw