Luttrell 2012
61
Name: ______________________
Date: _____
4e - Evaluating
Most times you need to determine the value of an expression (the number an expression
represents). In order to find the value, you need to know what the variables represent. By
substituting the value of the variables and simplifying, the value of the expression will be found.
Note the vertical alignment of the work; try to show your work in similar manner.
Example A: Evaluate the expression when
y
= 2:
3
y
+ 2
y
2
- 6(
y
- 4) + 8
y
3
.
Step I - substitute value of
y
. 3(2) + 2(2)
2
- 6(2 - 4) + 8(2)
3
.
Step II - simplify. 6 + 2(4) - 6(-2) + 8(8)
6 + 8 + 12 + 64
90
Example B: Evaluate
3 2
1
2
3
6
(
)
(
)
x
x
x
+ −
−
+
when
x
= -3
3 2
3
1
2
3
3
3
6
( (
)
)
(
)
− + − − −
− +
3
6
1
2
6
3
(
)
(
)
− + − −
3
5
12
3
(
)
− +
−
= −
3
3
1
Evaluate when a = -1.
1. (4a + 3)a - (2 + 2a)
2. 12a
2
- 3a + 2
3. 3a
4
+ 5a
3
- 6a
2
- 2a
Evaluate when
x
= 1,
y
= 2, and
w
= 2
4.
2
3
5
3
x
x
+ + −
5. -(-
x
)
6.
x
- (
x
- {
x - y
})
7. 4
w
+ 7 + 3
w
-2 + 2
w
8.
1
3
3
1
w
w
w
w
w
w
w
+ × +
× −
9.
3
2
5
(
)
(
)
x
y
x
y
x
y
+
−
−
+
