1.2 variables and expressions Objective: Be able to tell me what is all the parts of a variable expression. Be able to substitute a number for a variable and evaluate. Students will also be able to demonstrate how to construct a variable expression
Definitions Algebra: math that uses symbols. Variable: letter represents number. Ex: x and y Algebraic (variable) Expression: numbers, variables, and operations. Ex: 3x – 3y
Tell if examples are numerical, variable expressions or variables 3 – 4 + 3 X, Y, A 3x – 2 x 5 8y 4 – 9 3 + s
Evaluate Expression Key: put given #’s in for variables and solve. Ex: Given 2 + 5y and y = 2 Given 2y – 7 and y = 5
Student Examples Evaluate when x = 3
Evaluate 2 Variable Expressions Given x = 4 and y = 2, evaluate 3x + 2y Given 2x + 3x, evaluate when x = 5. Given 3a + 3b, solve when a = 5 and b = 7.
Student Examples Evaluate a = 8, b = 4 and c = 16 c – a bc b / a c – b b + c
Write as an algebraic expression 30 increased by a number. The quotient of 20 and a number The product of 50 and a number. Number of cars increased by 6
Write as algebraic expression 20 pieces of pizza divided by a group of people Two times as many. 6 feet shorter than the length of a bus. 8 dollars more for a bill.
Word Problem A studio charges a fee of $30 plus $5 for each portrait sheet ordered. Write an expression to find the total cost to have the pictures taken. Find the cost for 10 pictures.
Wrap – up Questions/Comments Ic: wkbk. Pg. 4 Hw: wkbk. Pg. 3