The gradient of a curve at any point. The single rule dxd(xn)=nxn−1 unlocks gradients, tangents, normals, and turning points — a recurring 5-7 mark item on Paper 4.
What you’ll learn
Mapped to the Cambridge IGCSE 0580 syllabus (2025-2027).
E2.14 — Use differentiation to find gradients of curves and the equations of tangents and normals; identify and classify stationary points.
The power rule
dxd(xn)=nxn−1. Bring the power down, decrease it by one.
The single most important rule:dxd(xn)=nxn−1.
Bring the power down to multiply, then decrease the power by 1.
Sum rule. Differentiate each term separately:
dxd(f+g)=dxdf+dxdg.
Worked. Differentiate y=2x3−5x2+4x−7.
dxdy=6x2−10x+4.
Negative and fractional powers. The same rule works.
dxd(x−2)=−2x−3.
dxd(x)=dxd(x1/2)=21x−1/2.
Bring power down, reduce by 1.
Constant: derivative is 0.
Differentiate term by term.
Negative and fractional powers: same rule, no change.
Gradient, tangent, normal
Substitute the x-value into the derivative for the gradient. Use it to write tangent or normal equations.
Gradient at a point. To find the gradient of a curve y=f(x) at x=a:
Compute dxdy.
Substitute x=a.
Worked. Find the gradient of y=x2+3x at x=2.
dxdy=2x+3.
At x=2: 2(2)+3=7.
Tangent line. Passes through the point and has the gradient you found.
y−y1=m(x−x1).
Worked. Find the tangent to y=x2+3x at x=2.
Point: y=4+6=10, so (2,10).
Gradient: 7.
Equation: y−10=7(x−2)⇒y=7x−4.
Normal line. Perpendicular to the tangent at the same point. Gradient of normal =−mtangent1.
Worked. Find the normal at the same point.
Normal gradient: −71.
Equation: y−10=−71(x−2).
The tangent has the curve's gradient; the normal meets it at a right angle.
Gradient at x=a: substitute a into dxdy.
Tangent: y−y1=m(x−x1).
Normal gradient: −1/mtangent.
Always find both the point AND the gradient before writing the equation.
Stationary points (turning points)
Where the gradient is zero. Use the second derivative or a sign change to classify max vs min.
Stationary points are where dxdy=0 — places where the curve momentarily has zero gradient.
Method to find them.
Differentiate to get dxdy.
Set dxdy=0 and solve.
Substitute each x-solution back into y to find the corresponding y-coordinate.
Method to classify them.
Second derivative test. Compute dx2d2y and substitute the x-coordinate.
dx2d2y>0: minimum.
dx2d2y<0: maximum.
Sign-change test. Check the gradient just before and just after the stationary point.
−,0,+: minimum.
+,0,−: maximum.
−,0,− or +,0,+: point of inflexion.
At both turning points the gradient is zero; the second derivative tells you which is which.
Worked. Find and classify stationary points of y=x3−6x2+9x+1.
dxdy=3x2−12x+9.
Set to zero: 3x2−12x+9=0⇒x2−4x+3=0⇒(x−1)(x−3)=0.
x=1 or x=3.
y-values: y(1)=1−6+9+1=5. y(3)=27−54+27+1=1.
dx2d2y=6x−12.
At x=1: 6−12=−6<0⇒ maximum at (1,5).
At x=3: 18−12=6>0⇒ minimum at (3,1).
Stationary points: dxdy=0.
Find y-coordinates by substituting back.
Second derivative: positive → min, negative → max.
Sign-change test as backup.
How it’s examined
Differentiation appears every Paper 4 as a 5-7 mark question — usually a polynomial whose stationary points need finding and classifying, sometimes with tangent/normal equations. Examiner reports flag forgetting to find y-coordinates of stationary points, and confusing maximum with minimum on the second-derivative test.
Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.
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Step-by-step worked examples — Differentiation
Step-by-step solutions to past-paper-style questions on differentiation, written exactly the way a tutor would explain them at the board.
1Differentiate a polynomial
Extended• differentiation
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Question
Differentiate y=4x3−5x2+7x−2 with respect to x.
Step-by-step solution
Step 1
Apply the power rule term by term: dxd(xn)=nxn−1.
dxdy=12x2−10x+7
Step 2
The constant −2 differentiates to 0.
Answer
dxdy=12x2−10x+7
2Find the gradient at a specific point
Extended• Adapted from 0580/42 May/Jun 2024 Q15• gradient
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Question
Find the gradient of y=x3−4x+1 at the point where x=2.
Step-by-step solution
Step 1
Differentiate.
dxdy=3x2−4
Step 2
Substitute x=2.
dxdyx=2=3(4)−4=8
Answer
Gradient =8
3Find the equation of a tangent
Extended• Adapted from 0580/42 Oct/Nov 2023 Q14• tangent
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Question
Find the equation of the tangent to y=x2−3x+2 at the point x=4.
Step-by-step solution
Step 1
Find y at x=4.
y=16−12+2=6.Point: (4,6)
Step 2
Differentiate.
dxdy=2x−3
Step 3
Gradient at x=4.
m=2(4)−3=5
Step 4
Use y−y1=m(x−x1).
y−6=5(x−4)⟹y=5x−14
Answer
y=5x−14
4Find and classify stationary points
Extended• stationary points
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Question
Find the stationary points of y=x3−6x2+9x+1 and classify them.
Step-by-step solution
Step 1
Differentiate and set to zero.
dxdy=3x2−12x+9=0
Step 2
Divide by 3 and factor.
x2−4x+3=0⟹(x−1)(x−3)=0
Step 3
Compute y for each.
x=1:y=5.x=3:y=1.
Step 4
Classify with the second derivative: dx2d2y=6x−12.
x=1:dx2d2y=−6<0⇒maximum.x=3:dx2d2y=6>0⇒minimum.
Answer
Maximum at (1,5); minimum at (3,1)
Examiner tip
Always classify using either the second-derivative test OR a sign-change check on dxdy. Stating "max" or "min" without justification loses marks.
5Differentiate y=3x4−2x2+7
Core• differentiation, power rule
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Question
Find dxdy for y=3x4−2x2+7.
Step-by-step solution
Step 1
Apply the power rule to each term: bring the index down, subtract one.
dxd(3x4)=12x3;dxd(−2x2)=−4x
Step 2
The constant 7 differentiates to 0.
Answer
dxdy=12x3−4x
6Differentiate a term with a negative index
Core• differentiation, negative index
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Question
Find dxdy for y=x2+x4.
Step-by-step solution
Step 1
Rewrite x4 as 4x−1.
y=x2+4x−1
Step 2
Apply the power rule to both terms.
dxdy=2x+4(−1)x−2=2x−x24
Answer
dxdy=2x−x24
Examiner tip
The examiner report flags candidates often drop the index manipulation and try to "differentiate the bottom". Rewrite as x−1 first; the power rule then applies normally.
7Equation of a tangent at a specific point
Extended• Adapted from 0580/42 Feb/Mar 2024 Q16• tangent
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Question
Find the equation of the tangent to y=2x2+x−4 at the point where x=−1.
Step-by-step solution
Step 1
Find y at x=−1.
y=2(1)+(−1)−4=−3.Point: (−1,−3)
Step 2
Differentiate.
dxdy=4x+1
Step 3
Gradient at x=−1.
m=4(−1)+1=−3
Step 4
Apply y−y1=m(x−x1).
y+3=−3(x+1)⟹y=−3x−6
Answer
y=−3x−6
8Find the point with a given gradient
Extended• gradient
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Question
On the curve y=x2−8x+5, find the coordinates of the point where the gradient is −2.
Step-by-step solution
Step 1
Differentiate.
dxdy=2x−8
Step 2
Set the derivative equal to −2 and solve.
2x−8=−2⟹x=3
Step 3
Find y.
y=9−24+5=−10
Answer
(3,−10)
9Real-world rate of change (kinematics)
Challenge• Adapted from 0580/42 May/Jun 2024 Q18• application, kinematics, rate of change
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Question
The displacement of a particle (in metres) at time t (in seconds) is s=t3−6t2+9t. Find (a) the velocity at t=4, (b) the time(s) when the particle is at rest.
Step-by-step solution
Step 1
Velocity = dtds.
v=3t2−12t+9
Step 2
(a) Substitute t=4.
v(4)=3(16)−48+9=9m/s
Step 3
(b) At rest: v=0.
3t2−12t+9=0⟹t2−4t+3=0
Step 4
Factor.
(t−1)(t−3)=0⟹t=1s ort=3s
Answer
(a) 9 m/s (b) t=1 s and t=3 s
Examiner tip
The examiner report flags candidates often confuse displacement and velocity. The first derivative of displacement gives velocity; "at rest" means v=0, not s=0.
For f(x)=x3−12x, find the intervals on which f is increasing and the intervals on which it is decreasing.
Step-by-step solution
Step 1
Differentiate.
f′(x)=3x2−12=3(x2−4)=3(x−2)(x+2)
Step 2
Sign analysis of f′(x):
x<−2:f′>0;−2<x<2:f′<0;x>2:f′>0
Step 3
Increasing where f′>0, decreasing where f′<0.
Answer
Increasing on x<−2 and x>2; decreasing on −2<x<2.
Examiner tip
The mark scheme awards a method mark for factorising f′(x) and another for the sign table. The examiner report flags candidates who skip the sign table and assert the answer.
Key Formulae — Differentiation
The formulae you need to memorise for differentiation on the Cambridge IGCSE 0580 paper, with every variable defined in plain English and a note on when to use it.
Power rule
dxd(xn)=nxn−1
n
any rational number
When to use
Differentiating any term of the form axn.
Sum / constant rules
dxd(f+g)=f′+g′,dxd(c)=0
c
any constant
When to use
Differentiate term by term; constants vanish.
Equation of a tangent at a point
y−y1=m(x−x1)
(x1,y1)
the point of contact on the curve
m
the gradient dxdy at x1
When to use
After computing the gradient at the point of tangency.
Second-derivative test
dx2d2y>0⇒min;dx2d2y<0⇒max
When to use
Classifying a stationary point once you've found its x-value.
Key Definitions and Keywords — Differentiation
Definitions to memorise and the exact keywords mark schemes credit for differentiation answers — sharpened from recent examiner reports for the 2026 0580 sitting.
Derivative
Examiner keyword
The function dxdy giving the gradient of the curve y at any point.
Gradient at a point
Examiner keyword
The numerical value of dxdy when a specific x is substituted in.
Tangent
Examiner keyword
A straight line that touches a curve at exactly one point with the same gradient as the curve there.
Stationary point
Examiner keyword
A point on the curve where dxdy=0 — local maximum, local minimum, or point of inflection.
Second derivative
The derivative of the derivative, written dx2d2y.
Common Mistakes and Misconceptions — Differentiation
The traps other students keep falling into on differentiation questions — taken from recent Cambridge IGCSE 0580 examiner reports and mark schemes — and how to avoid them.
✕Forgetting to decrement the power
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Why it happens
Students multiply by n but leave the power unchanged: dxd(x3)=3x3 instead of 3x2.
How to avoid it
Power rule has TWO parts: bring the index down AND subtract one from it.
✕Differentiating a constant to itself
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Why it happens
dxd(7)=7 instead of 0.
How to avoid it
Constants always differentiate to 0.
✕Stating "max" or "min" without justification
0580/42 — recurring
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Why it happens
Students see the shape from a sketch and assert.
How to avoid it
Always justify with the second-derivative test or a sign-change table.
✕Using the symbolic gradient dxdy instead of evaluating it at the point
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Why it happens
Students plug dxdy as the slope without substituting the x-value.
How to avoid it
Step 1 = differentiate. Step 2 = substitute the point's x to get a NUMBER. That number is the slope.
Practice questions
Exam-style questions with step-by-step worked solutions. Try one before checking the method.
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Differentiation — frequently asked questions
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