March 1, 2010 Math 201 OBJECTIVE: Students will be able to use substitution to evaluate algebraic expressions, including exponents of one, two, or three AIM: How can we use the order of operations to help us evaluate algebraic expressions? STANDARDS: 6.A.2 PRIOR KNOWLEDGE: Write as an algebraic expression Five more than some number, n Three less than some number times two

When we evaluate an expression, we SUBSTITUTE some value for the variable. “SUBSTITUTE” means “TO REPLACE” Example: n + 5, when n = 3 Rewrite the expression, and substitute for n 3 + 5 We can now evaluate the expression by doing the math: 3 + 5 is 8

Example: Evaluate n2 – 5, when n = 6 1. Rewrite, using substitution 2. Do the math, using order of operations 62 – 5 is the same as 36 – 5, which is 31 Example: Evaluate 5x2 + 9 (NOTE: the exponent goes with the variable ONLY) Rewrite, using substitution 2. Do the math using order of operations

Example: Evaluate 2y3 + 5, when y = 2 Rewrite, using substitution Do the math using order of operations

INDEPENDENT WORK What is the value of the expressions? n + 4 when n = 3 2y – 5 when y = 7 3n2 + 3 when n = 2 a3 when a = 3 2n2 – 6 when n = 5 HOMEWORK: Handout