FORMULAS AND EQUATIONS
(CS-4 math A_F 1.4, 1.5) teacher link
here
An expression or formula is string of letters
and symbols that tell us how to calculate something. An equation is like a
formula and tells us that the quantities separated by the equal symbol, =, are
the same. The letters can be any letters we choose to use but they should
indicate quantities of some kind. The symbols are called operators and
they tell is what calculations to perform. Here are five common
operators:
| + called plus | It means add |
| - called minus | It means subtract |
| x called times | It means multiply |
| / called divided by | It means divide |
| = called equals | It means the same |
Arithmetic Operators
These operators are the same ones used by a calculator.
Check it out:
Lets try some
examples. X = 2 + 2. This means that X is the same as 2 added
to 2. So what is the value of X? Who could we
ask?
Too easy you say. OK, lets try one that's a
little harder. This time we will also use
parentheses:
Suppose X = 3 and you are told that Y = (X+1) x (X-1)
What is the value of Y? Hint:
evaluate the expressions inside the parentheses first and then
multiply:
Remember our table with unknown length from the
previous page? We used a formula to calculate its area. The formula
was A = UL x UW. This tells us how to calculate the area of the table:
Multiply the length of the table by the width of the table and the result is the
area of the table.
An equation always tells us that two things are
equal. Y = 3X + 5 is an equation. Y is called the left side of
the equation. 3X + 5 is called the right side of the equation. 3X is
the same as 3 x X but is easier to write down. If we are given a
value for X we can calculate the value of Y which satisfies the equation. Satisfies means makes the equation true. For
example if we are told X=1 we can do the calculation and determine that Y=8
satisfies the equation but Y=7 does not. Finding the right value is called
solving the equation. One way to solve equations is to make a
table of X values and Y values which satisfy the equation. For
example:
Another way to solve equations is to use a
graph. You will learn lots more about graphing later. A graph allows
us to pick any value for X and read the correct value for Y from the
graph. Here is a graph of the equation Y = 3X + 5. The straight
lines are the axes of the graph
and the slanted line represents the equation. Looking at the graph, when X
= 0 what is the value of Y?
Feeling smart now? OK, try this:
Visit these web sites for more information and
practice with equations and formulas:
The Math
page
Basics of
Algebra
Solving Equations