1. Expressions and Equations
Targets:
1) Write & evaluate algebraic expressions.
2) Determine if a # is a solution of an equation.

2. Warm-Up

3. VOCAB Variable: Algebraic expression: Evaluate: Equation: Solution:
A letter that represents one or more numbers.
Algebraic expression:
contains numbers, operations, and variables
Does NOT have =
2N + 3
Evaluate:
Find the value
Equation:
2N + 3 = 5
Solution:
An answer that makes an equation true.

4. Evaluating an Expression
Rewrite the expression by substituting the given value(s) for the variable(s).
Follow the order of operations to find the value of the expression.

5. Example 1a Evaluate the algebraic expression. 5N – 3 when N = 8
Substitute 8 for N (8) – 3
Multiply – 3
Subtract

6. Example 1b Evaluate the algebraic expression.
(y + 2)2 + p when y = –7 and p = 9
Substitute –7 for y and 9 for p. (–7 + 2)2 + (9)
Add inside the parentheses (–5)2 + 9
Square
Add

7. Example 2 Write an algebraic expression for each phrase.
The product of seven and m 7m
Two less than six times x
2 + 6x or 6x + 2
Y divided by three then decreased by four

8. Example 3a Determine if the number given is the solution of the
equation.
–2y + 6 = – Is 5 the solution?
Substitute 5 for y –2(5) + 6 ≟ –16
Multiply – ≟ –16
Add – 4 ≠ –16
Five is not the solution.

9. Example 3b
Determine if the number given is the solution of the
equation.
Is 40 the solution?
Substitute 40 for x.
Divide.
Subtract.
Forty is the solution.
≟ 4
≟ 4

10. Exit Problems Evaluate when x = 24
Write an algebraic expression for the phrase “seven less than x”
Determine if 3 is the solution to the
equation 1 – 2x = 7

11. Communication Prompt
Why are variables used in mathematics?