### Home > CCA > Chapter 7 > Lesson 7.1.1 > Problem 7-8

If two expressions are equivalent, they can form an equation that is considered to be **always true**. For example, since .

If two expressions are equal only for certain values of the variable, they can form an equation that is considered to be **sometimes true**. For example, is equal to

*, so the equation*

If two expressions are not equal for any value of the variable, they can form an equation that is considered to be **never true**. For example, is not equal to

*for any value of*

*, so the equation*

*is said to be never true.*

Is the equation

The equation is sometimes true.

It is only true when *x* = 0.