Solving for Point D: How to Find the Intersection of Two Linear Equations

[hyde2042]

Homework Statement

The problem:

[2] http://i.imgur.com/C5VwZ.png

Homework Equations

So I got the constraints to be

1.x+y(less than or equal to) 275

2.225x+250y (less than or equal to) 63,000

3. x and y (Greater than) 0

So if the line from point A is extrapolated, then where it hits the x-axis would be constraint 2 and point C is constraint 1.

The Attempt at a Solution

The graph I ended up with:

[1] http://i.imgur.com/9jJYt.png

 

[Mark44]

Homework Statement

The problem:

[2] http://i.imgur.com/C5VwZ.png

Homework Equations

So I got the constraints to be

1.x+y(less than or equal to) 275

2.225x+250y (less than or equal to) 63,000

3. x and y (Greater than) 0

So if the line from point A is extrapolated, then where it hits the x-axis would be constraint 2 and point C is constraint 1.

The Attempt at a Solution

The graph I ended up with:

[1] http://i.imgur.com/9jJYt.png

Point D is where the line x + y = 275 intersects with the line 225x + 250y = 63000. This is a simple matter of solving a system of two equations in two unknowns.

The problem you posted in your first link seems to have nothing to do with what you're doing here.

 

[hyde2042]

Whoops. Sorry about the wrong post.

When I set the two equal to each other. -x + 275 = (225/250)x + (63000/250) I'm getting the incorrect answer.

The book says it should be (230, 45)

I keep getting (12.1, 262.9)

 

[Mark44]

Whoops. Sorry about the wrong post.

When I set the two equal to each other. -x + 275 = (225/250)x + (63000/250) I'm getting the incorrect answer.

You have a sign wrong in the right side. Solving the second equation for y gives y = -(225/250)x + 63000.

I get the right answer.

The book says it should be (230, 45)

I keep getting (12.1, 262.9)