91Ó°ÊÓ

A symbol we usually pick letters to be symbols, usually represents a number. Any letter you choose can be a variable.

A variable is a symbol that stands in for an unknown value in a mathematical expression. A variable expression is a combination of terms and mathematical operations that contains at least one variable. Example a + 2x + 10

An equation is a mathematical statement that two expressions are equal. The solution of an equation is the value that when substituted for the variable makes the equation a true statement.

Example: 3x + 5 = 14 is an equation, in which 3x+5 and 14 are two expressions separated by an ‘’equal’’ sign.

Solving the equation $−8·y=40$

$\begin{array}{l}−8·y=40\\ \frac{−8·y}{−8}=\frac{40}{−8}\text{Dividebothsidesbythecoefficient}(−8)\text{of}y\\ ⇒y=−5\end{array}$

The solution of the equation is

$y=−5$