1.2.1 – Algebraic Expressions,
PEMDAS
• You are familiar with equations…right?
• Algebraic expressions are similar, but no equal
signs (not solving for anything)
– Combination of variables (letter to represent one
or more numbers) and operations (+, -, etc.)
PEMDAS
• We will encounter numerous types of algebraic
expressions; some may be used to model real life
scenarios or situations
– 2x + 9
– 3(p – 7) + 10
• Before evaluating them, always must consider the
order of operations
– Gives us a guide on how to evaluate expressions
correctly
• PEMDAS
• P = parenthesis
– Always start on inner most set; work your way out
• E = exponents
– Always check signs
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M = multiplication
D = division
A = addition
S = subtraction
• Typically, after you substitute a value for a
variable, most follow the order of operations
to obtain the correct answer
• Example. Evaluate 3(x + 1) – 2 if x = 4
– What do you do with the x = 4 part?
• Example. Evaluate ((x + 2)/2) + 9 x 2 for x = 5
• Example. Evaluate -2 ∕2 + 6 x 4
• Example. Evaluate 4 – 3(7 + 2)
Powers
• With large scale multiplication, need a quick
way to complete it
– Multiplication is essentially fast hand addition
• We use powers for repeated multiplication
– Two parts;
– Base = factor being multiplied
– Exponent = numbers of times multiplied
– Example. 7 x 7 x 7 = 73
• With powers, always have to be careful about
negative signs and parenthesis (use our
knowledge of PEMDAS to help)
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Example. Evaluate the following expressions
A) 23
B) (-2)3
C) -23
• Example. Evaluate the following.
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A) -162
B) 63
C) -25
D) (-2)5
• Not all exponents are the same! Always be
aware of the negative sign
– It’s like a “-1”
– Using multiplication after exponents
• Example. Evaluate -4p2 + 4p – 2 if p = 2.
• Example. Evaluate 2x2 + 2x – 1 if x = -2.
• Assignment
• Pg. 12
• 15-19 odd, 21-27 odd, 33-39 odd, 48, 50, 54