Transcript Lesson 1-6: Writing Expressions

1-6 Writing Expressions
Objective (things to learn): With this section
you will need to learn how to evaluate variable
expressions.
Terms to Know
1. Variable-is a symbol or letter used to
represent a number.
2. Algebraic expression-is a collections of
numbers, variables, operations, and
grouping symbols.
1-6 Writing Expressions
The following is a list of Algebraic expressions
and there meanings:
Algebraic expressions
15y
7a
b
3m  6
Meanings
15 times y
7 times a, divided by b
3 times m, plus 6
1-6 Writing Expressions
Next, let’s look at how to evaluate some
algebraic expressions.
Example 1
Evaluate 3x + 7y when x = 4 and y = 2.
Solution: to evaluate this expression, simply substitute 4 for x
and 2 for y.
First, write the expression.
4
2 Then substitute 4 for x and 2
for y. Simplify 3(4) and 7(2).
Then add.
3x  7 y  3( )  7( )
 12  14
 26
SOLUTION
1-6 Writing Expressions
Let’s look at how to evaluate another
algebraic expressions.
Example 2
Evaluate x + (5x - 8) when x = 3.
Solution: to evaluate this expression, simply substitute 3 for
each x .
x  (5x  8)  3  (5  3)  8
 3  15  8
 3 7
 10
Substitute 3 for x twice.
Simplify 5·3.
Simplify 15 - 8.
SOLUTION
1-6 Writing Expressions
Remember, to evaluate an expression use
the following flow chart and show your
work!!!!
Write the
algebraic
expression.
Substitute
values for
variables.
Simplify the
numerical
expression.
1-6 Writing Expressions
Representing real life situations.
Recall: the Area of a rectangle is equal to the
length times the width. A = lw
Example 3
Suppose the length of a rectangle is 12in. and the
width of the rectangle is 5in.. What is the Area of
the rectangle?
Solution Use the formula A = lw
A = (12in.)(5in.)
= 60 sq. in.