MHB Understanding Parabolas: Equation of Axis of Symmetry Explained

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The discussion centers on finding the axis of symmetry for the parabola defined by the equation y=6(x+1)(x-5). The correct method involves using the intercepts, which are x = -1 and x = 5, leading to the calculation of the axis of symmetry as (−1 + 5)/2, resulting in 2. The confusion arose from misinterpreting the intercepts, with the participant initially calculating incorrectly. Clarification was provided that the intercepts correspond to the factors of the equation, emphasizing the importance of understanding the graph versus algebraic form. Ultimately, the correct axis of symmetry is confirmed to be 2.
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I've encountered a question that I need help understanding the answer to.

The question is:
What is the equation of the axis of symmetry of the parabola given by the equation y=6(x+1)(x-5)?

Now, I know this quadratic equation is in intercept form, and I know that the formula for finding the axis of symmetry for this is (p+q)/2

Which means that it's (1-5)/2
then -4/2
Which equals -2. But it says that the correct answer is 2, not -2.
I'm confused, is my formula wrong? Please help.
 
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That's because if $(x - a)$ is a factor of your equation, then the intercept is at $x = a$, not $x = -a$. So in fact your parabola has intercepts $x = -1$ and $x = 5$, and so you would get $\frac{-1 + 5}{2} = \frac{4}{2} = 2$ as expected. The formula itself is correct.

As an example, try plotting $y = x - 5$, and you'll see it intercepts the x-axis at $x = 5$, and not $x = -5$. In the same way, try plotting your parabola and see where it intercepts the x-axis.​
 
Ah, I forgot the rule for the x intercept. It's different when looking at a graph than it is in algebraic form. You've definitely helped me, thanks a bunch!
 
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