1. Graphing Equations With Two Variables
COURSE 3 LESSON 3-2
Determine whether each ordered pair is a solution of y = 2x + 8.
a. (4, 8)
y = 2x + 8
8 2(4) + 8
Substitute 8 for y.
Substitute 4 for x. = /
(4,8) is not a solution.
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2. Graphing Equations With Two Variables
COURSE 3 LESSON 3-2
(continued)
b. (–2, 4)
y = 2x + 8
4 2(–2) + 8
Substitute 4 for y.
Substitute –2 for x.
4 –4 + 8
4 = 4
(–2, 4) is a solution.
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3. Graphing Equations With Two Variables
COURSE 3 LESSON 3-2
The equation y = 12x + 5 describes the cost y in dollars to order x CDs from a catalog. Complete the solution (5, ? ). How much will it cost to buy 5 CDs?
Complete the solution (5, ? ) to find out how much 5 CDs will cost.
y = 12x + 5
= 12(5) + 5
Substitute 5 for x. =
Multiply.
= 65
Add.
A solution is (5, 65). It will cost $65 to buy 5 CDs.
Check for Reasonableness If it costs $65 to buy 5 CDs, the cost for
one CD is about or $13. $13 is a reasonable cost for a CD.
$65 5
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