1. write algebraic expressions by representing unknown quantities; and
Today we are going to:
write algebraic expressions by representing unknown quantities; and
evaluate algebraic expressions by substituting the given value for the variable.

2. ALGEBRAIC EXPRESSIONS
EVALUATING
ALGEBRAIC EXPRESSIONS

3. Write an algebraic expression for each of the following statements.
Add 3 to p
(b) Subtract 2 from the product of 3 and x
(c) Divide the sum of
m and n by 5
(d) Multiply 7 to half of t
p + 3
3x – 2
m + n 5 7t 2

4. Algebraic Expression in Two or more unknown
Example :
State the number of unknown in each of the
following algebraic expressions.
(a) 2a + 2b (b) 100 – 2pqr (c) hjk + 8p – 19q
Answer :
2a + 2b has two unknown : a and b
100 – 2pqr has three unknown : p, q and r
hjk + 8p – 19q has five unknown : h, j, k, p and q

5. Evaluating Algebraic Expression
*To evaluate an algebraic expression is to find the value of the expression.
STEPS:
1. Substitute the given value for the variables
(replace letters with the given numbers)
2. Solve using the order of operations (PEMDAS)

6. Example : Solution : 2x + 5y = 2 (4) + 5 (2) = 8 + 10 = 18
Evaluate 2x + 5y when x = 4 and
y = 2
Solution :
2x + 5y
= 2 (4) + 5 (2) =
= 18

7. Evaluate p+2q+ 3r given p = 2 q = 4, r = 6
=2+ 2(4) + 3(6) =
=28

8. Example : Evaluate 3c + 5 if c = 5 and d = 1 4d Solution := 4
= 20
= 5

9. ALGEBRAIC EXPRESSIONS
Step 1 Substitute the given values for the variables.
Step 2 Solve using the order of
Operations PEMDAS.

10. Given the formula P=2L+2W, find the value of P if K=7 and W=3.
Problem 1
Given the formula P=2L+2W, find the value of P if K=7 and W=3.

11. If V=lwh, what is the value of V when l=2, w=3, and h=4?
Problem 2
If V=lwh, what is the value of V when l=2, w=3, and h=4?

12. V=x 2h, find V when x=6 and h=2
Problem 5
Using the formula
V=x 2h, find V when x=6 and h=2

13. Problem 8
Find the value of
(x2-8x+4) if x=1/2.