Chapter 9 linear inequaliTieS 341
- 523 9
5
≤≤F and FC=+ 32.
5 9
5
32 23
32 32 32
27 9
5
9
5
9
27
1
5
9
9
5
≤+≤
---
-≤ ≤-
⋅- ≤⋅ ≤
C
C
C^55
9
9
1
15 5
⋅-
-≤≤-C
- Let x represent the saleswoman’s annual sales. Let s = 15, 000 + 0.10x rep-
resent her annual salary. She wants 40 000,,≤+15 000^01 .,^06 x≤^0000.
15,000
40 000 15 000 01060000
15 000
,,.,
,
≤+≤
--
x
- ≤≤
15 000
25 000 01045000
25
,
,. ,
,
x
0000
010
010
010
45 000
010
250 000 450 000
.
.
.
,
.
,,
≤≤
≤≤
x
x
She needs to have her annual sales range from $250,000 to $450,000
in order to maintain her annual salary between $40,000 and
$60,000.
- Let x represent the number of kilowatt-hours the Smiths use per month.
Then c = 20 + 0.12x represents their monthly electric bill.
80 20 012 110
20 20 20
≤+ ≤
-- -
. x
660 01290
60
012
012
012
90
012
500 750
≤≤
≤≤
≤≤
.
.
.
..
x
x
x
The Smiths would need to keep their monthly usage between 500 and
750 kilowatt-hours to keep their monthly bills in the $80 to $110
range.