Everyone. So let's take a look at this example problem we're working out together. We've got these three graphs that are showing these three pairs of lines, and we want to take these graphs and match them to their system of equations shown here below. So, really, I'm just going to try to match equations to graphs. Let's take a look at the first one over here because I've got y=3x+5 and y=-2x+10. Notice how both of these are in slope-intercept form. So it's going to be a little bit easier to sort of try to match the equation with the graph than, for example, this equation, which is a little bit messier. Alright? So let's take a look at 3x+5. I'm looking for something that crosses the y-axis here at positive 5. So let's take a look at this first graph over here. I'm looking for if anything crosses at y=5 points, and it actually doesn't. So neither of these two graphs do. What about this one? In fact, both of these actually cross at y=10 or y-intercept of 10. And over here, what I see is that the red equation does actually cross the axis at y-intercept of 5. Alright? But let's just double-check the next equation, where this says y=-2x+10. So now I'm looking for a y-intercept of positive 10. Remember, this is like y=mx+b. Looking for the b term, which is 10. And if you look here, the blue equation does actually cross here at y=10. So that means that this is probably going to be equations for the graph c over here that I'm looking at. But just to sort of triple check, what we're going to do here is we're going to look at this intersection point, and we're going to plug it into both of these equations here. So remember, we're just going to take a look here, and we're going to plug these x and y values into their equations and see if we get true statements for both of them. Alright? So if you bring this equation down, what this says is that 8=3×1+5, and 8 does in fact equal 3+5, so you just get 8=8, which is a true statement. If you do it for the bottom equation, for the blue equation, what you'll see is you're going to get 8=-2×1+10, and 8 does in fact equal -2+10 because that just equals 8 as well. So this is definitely going to be a true statement. Alright? So let's take a look at now the second equation or second pair of equations. I've got y=4x+8. So if you look through my graphs, what you're looking for is remember, this is going to be in slope-intercept form. So I'm looking for something that crosses the axis at a positive 8. So does anything cross the axis at positive 8? It actually does over here, so that might be actually be the answer.
Table of contents
- 0. Review of Algebra4h 16m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 6m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 19m
- 10. Combinatorics & Probability1h 45m
7. Systems of Equations & Matrices
Two Variable Systems of Linear Equations
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Two Variable Systems of Linear Equations practice set
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