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Need to Know
Need to Know

Differentiation

The rules you must have ready for the exam.

How to use this: say each rule in your head, then tap Show me to check.

Slope & the rule

3 rules
Rule 01

Slope of a line

m = (y₂-y₁)/(x₂-x₁). y=mx+c → slope m. ax+by+c=0 → m = -a/b.

Rule 02

The rule

y = xⁿ → dy/dx = n xⁿ⁻¹. Multiply by the power, reduce by 1. Constant → 0. dy/dx = slope.

Rule 03

Slope at a point

Differentiate, then substitute the x-value.

Tangents, points & unknowns

2 rules
Rule 04

Tangent

Need a point and a slope. Slope from dy/dx; equation y - y₁ = m(x - x₁).

Rule 05

Find a point / unknown

Set dy/dx equal to what you're told and solve. For an unknown letter, sub the known x and slope in.

Turning points & sketching

3 rules
Rule 06

Turning point & nature

dy/dx = 0 for the turning point. d²y/dx² > 0 → min; < 0 → max.

Rule 07

Increasing / decreasing

Increasing where dy/dx > 0; decreasing where dy/dx < 0.

Rule 08

Sketching

Find the roots (y = 0) and the turning point (dy/dx = 0). Mark them and draw the curve.

Motion

1 rule
Rule 09

Speed & acceleration

v = ds/dt [m/s]; a = d²s/dt² [m/s²]. Initial = t=0; at rest = ds/dt = 0.

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