Solve the following systems by graphing. 1) 2x + y = 5 and x...

Solve the following systems by graphing. 1) 2x + y = 5 and x - 3y = -8 2) 6x - 3y = -9 and 2x + 2y = -6 Solve the following systems by substitution 3) y = 5x - 3 and -x - 5y = -11 4) 2x - 6y = -24 and x = 5y - 22 Solve the following systems by elimination 5) -4x - 2y = -2 and 4x + 8y = -24 6) x - y = 11 and 2x + y = 19

Transcript

00:02 To solve by graphing, you start with a graph, and it needs to be in slope intercept form.

00:09 So solve for y, so i'm going to subtract 2x from both sides, and that's going to leave me with y equals negative 2x plus 5.

00:18 So i'm going to start with my y intercept.

00:20 1, 2, 3, 4, 5, and then i'm going to go down to 1, 2, over 1, down 2, over 1, down to, over one.

00:44 And that's going to be your line, your first line.

00:48 So the second line, i'm going to solve for y again.

00:51 So i'm going to subtract x on both sides.

00:54 So negative 3y equals negative x minus 8, divided by negative 3, all the way across.

01:04 So y equals 1 3rd x plus 8 over 3.

01:15 8 over 3 is, is equal to two and two thirds.

01:23 So start out at two and two thirds.

01:32 And then rise one, run three.

01:45 And it'll cross right there.

01:50 That point of intersection is your solution.

01:54 So the point of intersection looks like it's at one, three.

02:01 Three and that's how you solve by graphing so you should be able to do the next one make sure you're in slope intercept form first actually this one looks kind of crazy so let me put it in sleep intercept form for you so minus six x on both sides so negative three y equals negative six x minus nine divided by negative three all the way across so y equals two x plus three the next one, subtract 2x all the way across.

02:49 So 2y equals negative 2x minus 6, divide by 2.

02:56 Now i wouldn't funny.

02:59 So negative x, y equals negative x minus 3.

03:04 So now you can graph them both to find your solution.

03:09 Substitution.

03:12 Both of these are set up perfectly for supposed substitution.

03:14 So i'm going to do the first one.

03:16 So it equals y.

03:18 So i'm going to take what y is, and i'm going to replace it in the second equation.

03:23 So negative x minus 5 times 5x minus 3 because i'm replacing y with what y equals equals negative 1.

03:35 So negative x minus 25x plus 15 equals negative 11.

03:43 That should be 11 or there.

03:44 So negative x and negative 25x gives me negative 26x plus 15 equals negative 11, subtract 15 on both sides...

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