How do you know if an equation is always, sometimes, or never true?

If you try to solve the equation and one of the variables is suddenly eliminated, then you can see if it results in a true or false statement.

Start by simplifying both sides and then try plugging in different values to test it.

Simply put,

x=x

is an equation that is always true,

1=2

is an equation that is always false, and

x2=4

is an equation that is sometimes true.

Another example:

Try to solve 3 (2x+9) = 6x + 16. What happens? This equation has no solutions, because the variables cancel and you get 27 = 16, which is false. So this equation is never true