- [Instructor] We're told the system of linear equations
below is graphed on the coordinate grid.
Okay, we see that.
Then, it says: What is the value
of y equals -x - 7
when x is equal to -8.
So the graph y equals -x - 7,
that's this blue line here,
and they tell us, right?
That the point -8, 1 is on that line.
So when x is equal to -8,
y is equal to 1.
So we could type that in.
And then, they ask us:
What is the y-value of the bronze line
or the brown line here,
y is equal to 1/2x - 1
when x is equal to -8.
So we don't even have to compute it.
We see when x is equal to -8,
we get y is equal to -5,
so we put -5 there.
And then, they say:
Is x equal -8 a solution?
Well, the only way that x equals -8 would be a solution
is if the y value of those lines
when x equals -8 were the same,
but they're clearly not.
And in fact, we would see it visually.
If it was a solution,
the two lines would intersect at that point but they don't.
There's actually two different points here.
They don't overlap.
So this is not a solution
and we're done.