Vol. 1 · Algebra jigsaw

Factorization Techniques

A companion to 《因式分解技巧》 by Shan Zun · 13 stops ·

Vol. 1Vol. 2Vol. 3Vol. 4Vol. 5Vol. 6Vol. 7Vol. 8

  1. Ch. 0What Is Factorization?Write a polynomial as a product, like 60 = 2×2×3×5, until nothing splits.Concept
  2. Ch. 1Taking Out a Common FactorTake out what every term shares, all at once, and keep the 1s in the bracket.Skill
  3. Ch. 2Using the FormulasSquares and cubes, sums and differences: each formula is a picture to cut up.SkillM7
  4. Ch. 3Factoring by GroupingNo common factor overall? Group the terms so that the brackets match.Skill
  5. Ch. 4Splitting and Adding TermsOne term short of a formula? Add it and subtract it. Same value, open road.SkillM1
  6. Ch. 5The Cross MethodSplit the constant so that the cross products add up to the middle term.SkillM23
  7. Ch. 6Quadratics in Two VariablesTwo letters, six terms. Use three columns, and all three crosses must match.SkillM4
  8. Ch. 7Putting It All TogetherYou know the tools; the hard part is which one first. Ask in a fixed order.MethodM2M21
  9. Ch. 8Linear Factors of a PolynomialIf f(c) = 0, then (x − c) is a factor, and only a few rationals are worth a try.ConceptM23
  10. Ch. 9The Method of Undetermined CoefficientsGuess the shape of the factors with letters, multiply out, match, and solve.SkillM4
  11. Ch. 10Cyclic and Symmetric ExpressionsLetters swap seats but the expression stays put. One factor gives you the rest.ConceptM5M22
  12. Ch. 11Factoring over the Reals and the Complex Numbers“Cannot be split” depends on the numbers allowed. More numbers, finer factors.Concept
  13. Ch. 12Irreducible PolynomialsHow can you be sure nothing splits? Eisenstein's criterion uses a prime.Concept