3rd/5th/6th periods
https://www.khanacademy.org/math/algebra/quadratics
1st/2nd/4th period
https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-solving-equations
https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-solving-equations