Modern Algebra: A Logical Approach, Book Two c.1966
Chapter 6: Functions and Other Relations
Linear Inequalities
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(1) Draw the graph of the relation defined by each of the following sentences.
(a) y > -2*x + 3 y < x
y > -2*x + 3 y < x
Let's experiment a little. The objective here is to learn about linear inequalities while also gaining some technical skills using Sage. This is explortative learning at age 50.
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y > -2*x + 3 y < x
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y 7 y -3
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y 3 y x + 6 y -x - 3
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3x + y 5 -2x + y -4
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y x y 4
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[2] Draw the graph of the relation defined by each of the following sentences
(a) y > -2x - 5 y > -3x + 4
Changing this from a conjunction (intersection) to a disjunction (union):
(a) y > -2x - 5 y > -3x + 4
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(b) 3x + 1 > y y > -4x - 3
Changing this from a conjunction (intersection) to a disjunction (union):
(b) 3x + 1 > y y > -4x - 3
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(c) x >= 0 and y >= 0 y <= x + 4
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(d) y <= x + 4 y > -x - 2 and x > 0
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(e) y <= 4 x <= 3 y > -3 x > -3
(5) Given: A = {(x,y)| y <= -5x/3 + 7}, B = {(x,y)| y >= x - 1}, C = ((x,y)| y <= 9x + 39}, D = {(x,y)| y >= -7*x + 25},
draw the graph of:
(a) A B C
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(b) A B C D
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(6) If M = x - y, find the greatest possible value of M subject to the condition that (x,y) are coordinates of a point in A, the region which is the graph of {(x,y)| y <= -2*x/5 + 4} {(x,y)| y >= x - 3} {(x,y)| y >= 0} {(x,y)| x >= 0}
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(7) If K = -x/3 + y, find the least possible value of K subject to the condition that (x,y) are the coordinates of a point in B, the region which is the graph of {(x,y)| y >= -2x + 8} {(x,y)| y >= 2x/3}