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Detailed notes on Algebra for Cambridge IGCSE Mathematics, covering key concepts, explanations, examples, and exam-focused revision points.
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.
Mapped to the Cambridge IGCSE 0580 syllabus (2025-2027).
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.
Worked.
Coefficient rule. Constants pull through: dxd(kxn)=knxn−1.
Sum rule. Differentiate each term separately: dxd(f+g)=dxdf+dxdg.
Worked. Differentiate y=2x3−5x2+4x−7.
Negative and fractional powers. The same rule works.
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:
Worked. Find the gradient of y=x2+3x at x=2.
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.
Normal line. Perpendicular to the tangent at the same point. Gradient of normal =−mtangent1.
Worked. Find the normal at the same point.
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.
Method to classify them.
Worked. Find and classify stationary points of y=x3−6x2+9x+1.
Verbatim phrases and definitions Cambridge mark schemes credit.
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.
Sources: Cambridge IGCSE Mathematics 0580 syllabus 2025-2027 (E2.14); 0580/42 Oct/Nov 2024 — Q16 (stationary points); 0580 Examiner Reports 2022-2024. Last reviewed 2026-05-05.
Step-by-step solutions to past-paper-style questions on differentiation, written exactly the way a tutor would explain them at the board.
Almost every differentiation exam question is one of these shapes. Learn to spot each one and you will always know how to start.
Recognise it by
A single instruction — differentiate, find dxdy, find the gradient at x=a — handled with the power rule alone.
How to approach it
Apply dxd(xn)=nxn−1 to each term; rewrite fractions and roots as powers (x4=4x−1) first. To get a numerical gradient, substitute the x-value into the derivative.
Common trap
Bringing the index down but not subtracting one, or differentiating a constant to itself instead of 0. Examiner reports flag both as routine slips.
Recognise it by
Several stages chained — find a tangent (point, then gradient, then line), or find and classify stationary points, or determine increasing/decreasing intervals.
How to approach it
Differentiate first, then carry out the remaining stages in order: substitute for the gradient, classify with dx2d2y or a sign table, and use y−y1=m(x−x1) for a tangent.
Common trap
Stating "maximum" or "minimum" with no justification, or using the symbolic dxdy as a tangent's slope instead of evaluating it at the point.
Recognise it by
A real-world context — displacement, velocity, cost — with no derivative stated. You must recognise that a rate of change calls for differentiation.
How to approach it
Translate the context: the derivative of displacement is velocity, "at rest" means v=0. Differentiate, then substitute or solve as the question requires.
Common trap
Confusing displacement with velocity — setting s=0 for "at rest" instead of v=0. Examiner reports flag this every series.
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
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
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
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.
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
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.
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
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)
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=9 m/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=1 s or t=3 s
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.
Question
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.
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.
dxd(xn)=nxn−1
When to use
Differentiating any term of the form axn.
dxd(f+g)=f′+g′,dxd(c)=0
When to use
Differentiate term by term; constants vanish.
y−y1=m(x−x1)
When to use
After computing the gradient at the point of tangency.
dx2d2y>0⇒min; dx2d2y<0⇒max
When to use
Classifying a stationary point once you've found its x-value.
Definitions to memorise and the exact keywords mark schemes credit for differentiation answers — sharpened from recent examiner reports for the 2026 0580 sitting.
The function dxdy giving the gradient of the curve y at any point.
The numerical value of dxdy when a specific x is substituted in.
A straight line that touches a curve at exactly one point with the same gradient as the curve there.
A point on the curve where dxdy=0 — local maximum, local minimum, or point of inflection.
The derivative of the derivative, written dx2d2y.
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.
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.
Why it happens
dxd(7)=7 instead of 0.
How to avoid it
Constants always differentiate to 0.
0580/42 — recurring
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.
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.
The things students keep getting wrong in this sub-topic, answered.