Algebra: Variables and Expressions A variable is a letter or symbol that represents an unknown quantity (a number). The branch of mathematics that involves expressions with variables is called ALGEBRA. An ALGEBRAIC EXPRESSION is an expression that contains variables, numbers, and at least one operation. Objective: Learn to evaluate simple algebraic expressions.

An example of an algebraic expression Examples: N + 2 15 – C 6R = means 6 times R ( When a letter and a number are together with no sign in the middle, you must multiply. In algebra the multiplication sign is often omitted.) The number in a multiplication expression that contains a variable is called a coefficient, So 6 is the coefficient of 6R.

Examples: Evaluate N + 3 if N = 4. 4 + 3 7 Evaluate each expression if C= 8 and R = 5. 1. C – 3 2. 15 – C 3. C + R 4. 6R

Evaluate: 8W – 2V if W= 5 and V = 3. 8(5) – 2(3) 40 - 6 34 Evaluate: 4y2 + 2 if y = 3 4(3)2 + 2 4(9) + 2 36 + 2 38

Your examples: Evaluate each expression if a = 4 and b = 3. 9a – 6b 3. 2a2 + 5 2. ab 4. 6a – b 2

Homework: Evaluate each expression if d = 8, e = 3, f = 4, and g = 1. 2 10. (5d – 25) 5 16 f 12. e2 +4 d + 9 10 – e 4f + 1 8g – 3 f – e d + f 10g – 6