Deciding the Factorisation Method Flashcards

All 6 cards in this deck

Whatever the expression, what is the first thing to check before choosing a factorising method?

Whether every term has a common factor — take it out first.

Which method do you use for an expression of two terms that are both squares with a minus between them?

e.g. $p^2 - 49$

The difference of two squares: $(p - 7)(p + 7)$

Which method do you use for an expression of four terms with no factor common to all of them?

e.g. $ax + bx - ay - by$

Factorising by grouping: $(a + b)(x - y)$

Which method do you use for a three-term quadratic $ax^2 + bx + c$ where $a \neq 1$?

e.g. $6x^2 - 5x - 4$

Split the middle term using two numbers with product $ac$ and sum $b$, then group: $(2x + 1)(3x - 4)$

True or false? Once you have taken out a common factor, the factorisation is complete.

False. You must check whether the bracket factorises further.

e.g. $2m^2 - 2 = 2(m^2 - 1) = 2(m - 1)(m + 1)$

How can you check that a factorisation is correct?

Expand the brackets again and check you get the original expression.