Algebra 1

4 marks · Hard

Let .

(a)

Write in its simplest form.

[2 marks]

(b)

Find the value of when and .

[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) 6a - 4b

(b) -14

Common mistakes: Not collecting like terms correctly; Incorrect substitution for negative values

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Identifies and collects like terms for 'a' or 'b'.

A1 (a) · 1 mark · Fully simplifies to the correct form .

M2 (b) · 1 mark · Substitutes , correctly into their expression. (follow-through)

A2 (b) · 1 mark · Accurately calculates s = -14. (follow-through)

Worked solution

a) Collect like terms for 'a' and for 'b':

So .

b) Substitute and :