Algebra 3

4 marks · Normal

Expand and then fully factorise the following expression:

(a)

[2 marks]

(b)

Now, factorise completely:

[2 marks]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) x^2 + 2x - 15

(b) (x + 5)(x - 3)

Common mistakes: Incorrect expansion; Factors with sign errors

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Expands (x+5)(x−3) correctly to form quadratic

A1 (a) · 1 mark · All signs and terms correct in expansion

M2 (b) · 1 mark · Attempts to factorise given quadratic

A2 (b) · 1 mark · Both brackets correct: (x+5)(x−3), order unimportant

Worked solution

a) Expand:

b) Factorising : Need two numbers that multiply to -15 and add to 2. These are 5 and -3.