This key facts covers The Gradient Rules 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 5 of 9 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 5 of 9
Practice
14 questions
Recall
12 flashcards
The Gradient Rules
For Parallel Lines
If L₁ has gradient m₁ and L₂ has gradient m₂, then:
L₁ || L₂ ⟺ m₁ = m₂
For Perpendicular Lines
If L₁ has gradient m₁ and L₂ has gradient m₂, then:
L₁ ⊥ L₂ ⟺ m₁ × m₂ = -1
This means: m₂ = -1/m₁