The equation is .

Apply addition property of equality: Add 80 to each side.

         (Apply additive identity property: 0 + 80 = 80)

                         (Apply additive inverse property: )

Apply division property of equality: Divide each side by negative 2.

                           (Cancel common terms)

                           (Divide: )

                 (Take square roots of each side)

Rewrite the expression using product property of square roots;

For nonnegative real numbers a and b, .

Rewrite the () using imaginary unit; that is where .

Find the square root:

                        (Simplify)

The value of x.