Some Edexcel questions open with "In this question you must show all stages of your working." Underneath it is a second sentence, and there are two different versions of that sentence. They look almost the same. They do not mean the same thing.

Getting this wrong is one of the few ways to answer a question completely correctly and score nothing at all.

Not with Edexcel? We have the same guide for OCR and AQA. Every board has its own phrase for this and they do not mean quite the same thing.

In this guide

There are two versions, and one word separates them

Edexcel publishes a short guide explaining the difference. The two sentences are:

Solutions relying entirely on calculator technology are not acceptable.

and

Solutions relying on calculator technology are not acceptable.

The only difference is the word entirely, and it changes what you are allowed to do.

  • With "entirely" — you may use the calculator to help you along, but it must not solve the problem for you.
  • Without "entirely" — the stronger version. You must show all workings and calculations. The calculator is not helping you answer this one.

Read the second sentence, not just the first. Students see "show all stages of your working", assume they know what that means, and never notice which of the two versions follows it.

What you may still use the calculator for

On the "entirely" version, Edexcel gives examples of what is fine:

  • Working out a numerical expression
  • Finding a square root
  • Inverse trigonometry
  • Evaluating logarithms

And what is not:

  • Using graphing to solve a problem, such as finding where two lines cross
  • Using the calculator to integrate or differentiate
  • Using it to solve a cubic

The line is between processing and solving. Arithmetic is processing. Finding the roots of an equation is solving.

On the stronger version, Edexcel says it turns up on questions like solving quadratic equations and inequalities, finding exact solutions to trigonometric equations, factorising and solving cubics, and equations involving surds and indices.

Why one missing line costs four marks

This is the part worth understanding properly, because it explains why the penalty is so heavy.

Edexcel marks in three types. M marks are for method. A marks are for accuracy. B marks stand on their own.

The rule that bites is this one, in Edexcel's own words:

Accuracy marks can only be awarded if the relevant method (M) marks have been earned.

So if you skip the method and write the answer, the method mark goes. And because the accuracy marks depend on it, they go too. A four-mark question can become a zero-mark question on a page where every number you wrote was right.

Edexcel's guidance works exactly this through. A question solved properly scores M1 A1 dM1 A1. The same two correct answers, obtained on a calculator with no working, score M0 A0 dM0 A0.

A worked example

Suppose you are asked to solve

\[ 4^{x} - 5\left(2^{x}\right) + 4 = 0 \]

A calculator with an equation solver may well hand you \( x = 0 \) and \( x = 2 \). Both are right. With no working, on a question carrying this instruction, they are worth nothing.

What is wanted is the substitution that turns it into something you can factorise. Writing \( y = 2^{x} \), and noting that \( 4^{x} = \left(2^{x}\right)^{2} = y^{2} \):

\[ y^{2} - 5y + 4 = 0 \]

\[ (y - 1)(y - 4) = 0 \]

\[ y = 1 \quad \text{or} \quad y = 4 \]

Then back to \( x \):

\[ 2^{x} = 1 \Rightarrow x = 0 \qquad 2^{x} = 4 \Rightarrow x = 2 \]

Every line there is a mark or part of one. The substitution is the step the question is testing, and it is the step a calculator hides.

This is not an invitation to write an essay

Worth saying, because students who have been taught on another board sometimes over-correct.

Edexcel has no marks for explaining. Unlike some boards, there is no mark type for an explanation or for reasoning anywhere in Edexcel A Level Maths. Writing a paragraph about why you chose a substitution earns you nothing.

What earns marks is the algebra, written down, in order. Show the line where you substituted. Show the factorised form. Show the equation you solved. That is the working the instruction is asking for.

One habit that helps everywhere: do one process per line. Combining three steps into one line makes it harder for you to spot your own mistake and harder for the examiner to see the step that earns the mark.

A checklist for the exam

  • Read the sentence under the instruction and check whether it says "entirely".
  • Write the step the question is testing. If it is a disguised quadratic, the substitution must appear. If it is a cubic, the factorisation must appear.
  • Use the calculator to check your answer, not to find it. Checking is always sensible.
  • Do not write explanations. Write mathematics.
  • If an exact answer is asked for, leave it exact. Edexcel says marks are normally lost when a candidate resorts to rounded decimals where surds were wanted.

Go to the source. Edexcel publishes a short guide called "Calculator Instructions Guidance" explaining both versions of the sentence, with examples from real papers marked through. It is free on their website and takes ten minutes to read.