What is the fifth step in solving this equation by completing the square 9x2-6x 80?

Answer 1

Without the inclusion of an equality sign and not knowing the plus or minus value of 80 the expression can not be considered to be an equation.

But if you meant: 9x2-6x-80 = 0 then (3x+8)(3x-10) = 0 when factored

And its solutions are: x = -8/3 and x = 10/3