SOLUTION: 4x + 3y greater than or equal to 30 x + 3y greater than or equal to 21 x greater than or equal to 0 , y greater than or equal to 0 minimum for: C = 5x + 8y x + y grea

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Question 802751: 4x + 3y greater than or equal to 30
x + 3y greater than or equal to 21
x greater than or equal to 0 , y greater than or equal to 0
minimum for: C = 5x + 8y

x + y greater than or equal to 8
x + 5y greater than or equal to 20
x greater than or equal to 0, y greater than or equal to 0
Minimum for: C = 3x + 4y
1. Rewrite the constraints in slope-intercept form
2. List all vertices of the feasible region as ordered pairs.
3. List the values of the objective function for each vertex.
4. List the maximum or minimum amount, including the x, and y-value, of the objective
function.
I am stuck in this two questions I really do not know how to do them.

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
For the first problem, the constraints are:
4x+%2B+3y+%3E=+30
x+%2B+3y+%3E=+21
x+%3E=+0 , y+%3E=+0
The objective function and goal are:
minimum for: C = 5x + 8y

Following the step-by-step instructions:

1) The boundary lines to put in slope-intercept form are
4x+%2B+3y+=+30 --> 3y=-4x%2B30 --> y=%28-4%2F3%29x%2B10 and
x+%2B+3y+=+21 --> 3y=-x%2B21 --> y=%28-1%2F3%29x%2B7, because
x=0 does not have a slope, and
there is nothing to change in y=0, with slope=intercept=0.
Maybe you were expected to make the inequalities into something that we could call slope-intercept form:
4x+%2B+3y+%3E=+30 --> 3y%3E=-4x%2B30 --> y%3E=%28-4%2F3%29x%2B10 and
x+%2B+3y+%3E=+21 --> 3y%3E=-x%2B21 --> y%3E=%28-1%2F3%29x%2B7

2) You need to graph (or at least sketch) the feasible region satisfying all those constraints.
y%3E=%28-4%2F3%29x%2B10 means the line y=%28-4%2F3%29x%2B10 and all points above it.
y%3E=%28-1%2F3%29x%2B7 means the line y=%28-1%2F3%29x%2B7 and all points above it.
y%3E=0 means the line y=0 (the x-axis) and all points above it.
x%3E=0 means the line x=0 (the y-axis) and all points to the right of the y-axis.
The feasible region is the bubbly region at right and the blue bubbles mark the vertices.
The vertices are the points where the boundary lines cross at the edges of the feasible region:
system%28x=0%2Cy=%28-4%2F3%29x%2B10%29 --> system%28x=0%2Cy=10%29 --> highlight%28A%280%2C10%29%29
system%28y=%28-1%2F3%29x%2B7%2Cy=%28-4%2F3%29x%2B10%29 or better system%28x%2B3y=21%2C4x%2B3y=30%29 --> system%28x=3%2Cy=6%29 --> highlight%28B%283%2C6%29%29
system%28y=%28-1%2F3%29x%2B7%2Cy=0%29 or better system%28x%2B3y=21%2Cy=0%29 --> system%28x=21%2Cy=0%29 --> highlight%28C%2821%2C0%29%29

3) C%28x%2Cy%29=5x%2B8y
At A(0,10), C%280%2C10%29=5%2A0%2B8%2A10=80
At B(3,6), C%283%2C6%29=5%2A3%2B8%2A6=15%2B48=63
At C(21,0), C%2821%2C0%29=5%2A21%2B8%2A0=105

4) The minimum is C=highlight%2863%29 at point highlight%28B%283%2C6%29%29

The second problem is solved similarly:
The boundary lines are
x+%2B+y+=+8 , x+%2B+5y+=20 , and the x and y-axes
x+%2B+y+%3E=+8 --> y%3E=-x%2B8
x+%2B+5y+%3E=20 --> y%3E=%28-1%2F5%29x%2B4

The vertices of the feasible region are:
A%280%2C8%29, the solution to system%28x=0%2Cx%2By=8%29,
B%285%2C3%29, the solution to system%28x%2B5y=20%2Cx%2By=8%29, and
C%2820%2C0%29, the solution to system%28x%2B5y=20%2Cy=0%29
The objective function is C+=+3x+%2B+4y and the values at the vertices of the feasible region are:
At A, C+=+3%2A0+%2B+4%2A8=32
At B, C+=+3%2A5+%2B+4%2A3=15%2B12=27
At A, C+=+3%2A20+%2B+4%2A0=60
The minimum is C=highlight%2827%29 at point highlight%28B%285%2C3%29%29