Is x = 2 a solution to the equation x2 = 3x?
If we write down (2)2 = 3(2), we're lying. Sorry. We'll never do it again.
Let's figure out, without lying, if x = 2 is a solution to the equation.
First evaluate the left-hand side expression for x = 2:
(2)2 = 4
Then evaluate the right-hand side expression for x = 2:
3(2) = 6
Because 4 doesn't equal 6, x = 2 is not a solution to the equation x2 = 3x. Ah. It feels oh-so-much better to arrive at the answer honestly, doesn't it?