Chapter 11: Algebraic Expressions
6 lessons
Algebraic Expressions covers multiplying expressions together — monomial by monomial, monomial by polynomial, binomial by binomial — plus the standard identities, like (a+b)²=a²+2ab+b², that make many of these multiplications much faster. (x+3)(x+5), multiplied term by term, gives x²+8x+15 — the same result the identity (x+a)(x+b)=x²+(a+b)x+ab produces in one line.
The reverse is coming next
Factorisation, the very next chapter, is essentially this chapter run backward — a student can't factorise confidently without first being fluent at expanding.
Forgetting the middle term when expanding a square — writing (a+b)² as a²+b² instead of a²+2ab+b² — is the classic mistake here, alongside sign errors when multiplying binomials with mixed positive and negative terms.