equation:
slope:
yint:
y =
–
5x + 20
–
5
20
y =
4x + 5
4
5
y =
–
2x + 15
–
2
15
What is SLOPE?
x
the change in y divided by the
change in x
o
y = –5x + 20
o
x increases from 1 to 2
o
y decreases from 15 to 10
o
slope:
5
1
5
1
2
15
10
0
0
0
0
x
positive slope:
x and y increase
and decrease together
x
negative slope:
x and y
increase and decrease inversely
(when one rises the other falls)
Math – tool of
econ. analysis
NB: in linear functions (such as the
ones here) the slope equals the value
of the parameter by the variable X.
x
Why does curve slope up?
x
When is avg. consumption
greater than avg. income?
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 Fall '10
 willis
 Slope, Household income in the United States

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