Additional Mathematics – Straight-line graphs | e-Consult
Straight-line graphs (1 questions)
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First find the gradient of the second line.
Rewrite 3x + 4y = 12 as y = -(3/4)x + 3. Hence its gradient is m₂ = -3/4.
Let the gradient of the first line be m₁ = m.
- Parallel:
m₁ = m₂ ⇒ m = -3/4. - Perpendicular:
m₁·m₂ = -1 ⇒ m·(-3/4) = -1 ⇒ m = 4/3.
Therefore, m = -3/4 gives parallel lines, and m = 4/3 gives perpendicular lines.