### Video Transcript

A standard parabola in the 𝑥- and
𝑦-coordinate plane intersects the 𝑥-axis at four, zero and negative four,
zero. What is the value of the
𝑥-coordinate of this parabola’s line of symmetry?

So what I’ve done to help us answer
this question is drawn a sketch. And this is a sketch of our
parabola. A parabola is like this. So it’s either a u- or an
n-shape. So I’ve now sketched on the
n-shape. So what we know is what we have a
parabola. And what we want to do is find the
value of the 𝑥-coordinate of this parabola, where its line of symmetry is.

Well, from our sketch, it looks
like our line of symmetry is gonna go directly down the 𝑦-axis. So it’s going to be where 𝑥 is
equal to zero. So let’s test this and let’s work
it out.

So what we want to do is find the
midpoint between negative four and four, because the midpoint is going to be where
the line of symmetry is going to be. To do that, we’re gonna add
together four and negative four. And then we’re gonna divide it by
two, because this will give us the midpoint of the line between negative four and
four.

Well, when we work this out, the
answer is going to be zero. And that’s because we have
four. And then you add negative four. It’s the same as subtracting four
from four, which is just zero. And zero divided by two is still
zero.

So therefore, we can say that the
𝑥-coordinate of the parabola’s line of symmetry is going to be zero. And we’ve shown this through our
sketch, but also through the calculation.