•  Good online resources by topics:
     
      http://patrickjmt.com for great videos of math problems being worked out step by step.
      https://www.khanacademy.org/  wonderful lessons by topics
     
     
     
    After 1.4B and before Section 1.5 (Parametric Relations and Inverses), please watch these videos:  Part 1 (11:07 minutes) and Part 2 (9:45 minutes)