Multiply by .

Subtract from both sides of the equation.

Factor out of .

Factor out of .

Factor out of .

Divide each term in by .

Cancel the common factor of .

Cancel the common factor.

Divide by .

Move the negative in front of the fraction.

To rewrite as a function of , write the equation so that is by itself on one side of the equal sign and an expression involving only is on the other side.

Write as a Function of a a(n)=4n-20