Graphs 1
3 marks · NormalFind the equation of the straight line that passes through the points (1, 5) and (3, 9). Give your answer in the form y = mx + c.
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
y = 2x + 3
Must show: Gradient calculated correctly, Substitution for c, Final answer y = 2x + 3
Common mistakes: Substituting values incorrectly
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Calculates gradient: m = (9-5)/(3-1) = 2
M2 · 1 mark · Uses point and m to form y = mx + c, finds c = 3
A1 · 1 mark · Final answer y = 2x + 3 (follow-through)
Worked solution
Gradient: m = (9 – 5)/(3 – 1) = 4/2 = 2
Substitute (1, 5) into y = mx + c: 5 = 2 × 1 + c ⇒ c = 3