Graphs 2
3 marks · NormalFind the equation of a straight line with a gradient of $-3$ that passes through the point (2, 7). Write your answer in the form $y = mx + c$.
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Show answer
y = -3x + 13
Also accept: y=-3x+13; y = -3x + 13.0; y= -3x + 13
Common mistakes: y = -3x - 13; y = 3x + 7
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Substitutes the point into $y = -3x + c$ to form an equation.
M2 · 1 mark · Solves for c using the substituted point.
A1 · 1 mark · Writes the final equation correctly as $y = -3x + 13$.
Worked solution
Start with $y = mx + c$, $m = -3$, so $y = -3x + c$.
Substitute (2, 7): $7 = -3(2) + c$ ⇒ $7 = -6 + c$ ⇒ $c = 13$.
So the required equation is $y = -3x + 13$.