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- [Instructor] We're told the[br]system of linear equations

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below is graphed on the coordinate grid.

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Okay, we see that.

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Then, it says: What is the value

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of y equals -x - 7

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when x is equal to -8.

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So the graph y equals -x - 7,

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that's this blue line here,

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and they tell us, right?

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That the point -8, 1 is on that line.

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So when x is equal to -8,

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y is equal to 1.

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So we could type that in.

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And then, they ask us:

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What is the y-value of the bronze line

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or the brown line here,

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y is equal to 1/2x - 1

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when x is equal to -8.

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So we don't even have to compute it.

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We see when x is equal to -8,

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we get y is equal to -5,

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so we put -5 there.

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And then, they say:

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Is x equal -8 a solution?

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Well, the only way that x[br]equals -8 would be a solution

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is if the y value of those lines

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when x equals -8 were the same,

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but they're clearly not.

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And in fact, we would see it visually.

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If it was a solution,

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the two lines would intersect[br]at that point but they don't.

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There's actually two[br]different points here.

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They don't overlap.

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So this is not a solution

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and we're done.