Home / CIE iGCSE Maths E3.5 Equations of linear graphs Exam Style Practice Questions- Paper 2

CIE iGCSE Maths E3.5 Equations of linear graphs Exam Style Practice Questions- Paper 2

Question

(a) Find the gradient of line l.

(b) Find the equation of line l in the form y = mx + c.

(c) Find the equation of the line that is perpendicular to line l and passes through the point (12, -7). Give your answer in the form y = mx + c.

▶️ Answer/Explanation
Solution

(a) -3/4 or -0.75

Gradient = rise/run = -3/4

(b) y = -3/4x + 2

Using y-intercept at (0,2) and gradient from (a)

(c) y = 4/3x – 23

Perpendicular gradient = 4/3 (negative reciprocal). Substituted (12,-7) into y=4/3x+c to find c.

Question

Graph showing points A and B

A is the point (-6, 5) and B is the point (-2, -3).

(a) Find the equation of the straight line, l, that passes through point A and point B. Give your answer in the form y = mx + c.

(b) Find the equation of the line that is perpendicular to l and passes through the origin.

▶️ Answer/Explanation
Answers:
(a) \( y = -2x – 7 \)
(b) \( y = \frac{1}{2}x \)

Explanation:
(a) Equation of line AB:
1. Find slope (m): \( m = \frac{y_2 – y_1}{x_2 – x_1} = \frac{-3 – 5}{-2 – (-6)} = \frac{-8}{4} = -2 \).
2. Find y-intercept (c): Using point A (-6, 5), substitute into \( y = mx + c \):
\( 5 = -2(-6) + c \) → \( c = -7 \).
3. Final equation: \( y = -2x – 7 \).

(b) Perpendicular line through origin:
1. Slope of perpendicular line: Negative reciprocal of -2 → \( \frac{1}{2} \).
2. Since it passes through (0,0): \( y = \frac{1}{2}x \) (no y-intercept term needed).

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