Euler substitution

Euler Substitution is a way of solving equations with variable terms, like numbers and letters. To do Euler substitution you first write out the equation and then you look for terms (like x) that appear on both sides of the equal sign (=). Then you replace those terms with special symbols - like psi (ψ). Finally you solve the equation with the special symbols and then you can switch them back for the original terms. This way, it is easier to do the math and figure out what the answer is.