Juan wrote the proof below. What was his mistake?

Do not comment if you aren’t going to . create a real-life situation and create a system and show how it might be modeled algebraically with a system of equations (or inequalities) show all work include a few sentences explaining the situation, your variables of choice and what each represents, and how you would set it up and solve it algebraically. !

Use the x-intercept method to find all real solutions of the equation.x^3-10x^2+27x-18=0

Which of the following parabolas opens down?