GraphsDeep Dive

Worked Examples

Part of Parallel & PerpendicularGCSE Mathematics

This deep dive covers Worked Examples within Parallel & Perpendicular for GCSE Mathematics. Revise Parallel & Perpendicular in Graphs for GCSE Mathematics with 14 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 7 of 9 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 7 of 9

Practice

14 questions

Recall

12 flashcards

Worked Examples

Example 1: Parallel Line

Find the equation of the line parallel to y = 3x - 2 that passes through (1, 5).

Solution:

  1. Original gradient: m = 3
  2. Parallel line has same gradient: m = 3
  3. Using point (1, 5): 5 = 3(1) + c
  4. So c = 2
  5. Equation: y = 3x + 2

Example 2: Perpendicular Line

Find the equation of the line perpendicular to y = -2x + 7 that passes through (4, -1).

Solution:

  1. Original gradient: m₁ = -2
  2. Perpendicular gradient: m₂ = -1/(-2) = 1/2
  3. Using point (4, -1): -1 = (1/2)(4) + c
  4. So: -1 = 2 + c, therefore c = -3
  5. Equation: y = (1/2)x - 3

Example 3: Checking Perpendicular

Are the lines y = 3x + 1 and y = (-1/3)x + 5 perpendicular?

Solution:

  1. Gradients: m₁ = 3 and m₂ = -1/3
  2. Check: m₁ × m₂ = 3 × (-1/3) = -1 ✓
  3. Yes, they are perpendicular

Keep building this topic

Read this section alongside the surrounding pages in Parallel & Perpendicular. That gives you the full topic sequence instead of a single isolated revision point.

Practice Questions for Parallel & Perpendicular

Which of the following is true about two parallel straight lines?

  • A. They have the same gradient but different y-intercepts
  • B. Their gradients multiply to give -1
  • C. They have the same gradient and the same y-intercept
  • D. One gradient is the negative of the other
1 markfoundation

Explain why a horizontal line and a vertical line are always perpendicular to each other. Your explanation must refer to gradients.

2 marksstandard

Quick Recall Flashcards

What is the gradient rule for parallel lines?
Parallel lines have equal gradients. If L1 has gradient m1 and L2 has gradient m2, then L1 || L2 means m1 = m2.
What is the gradient rule for perpendicular lines?
Perpendicular lines have gradients that multiply to -1. If L1 perp L2 then m1 x m2 = -1.

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