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Before the midterm

Dropping a term of the expression

The habit: Substitute into every part and carry each piece through to the end, constants included.

64 practice questions are built to catch it, in 17 topics.

Practise against it: 6 questions

What it looks like

A question from the definition of the derivative, with the answer this slip gives beside the right one.

Standard3 marks · 4 min

Use the limit definition of the derivative to find f′(3)f'(3) for f(x)=x2−4xf(x) = x^{2} - 4x.

f′(a)=lim⁡h→0f(a+h)−f(a)hf'(a) = \lim_{h \to 0} \frac{f(a + h) - f(a)}{h}

Rules such as the power rule earn no marks on this question.

With the slip
6\displaystyle 6
Worked through
f′(3)=2\displaystyle f'(3) = 2

−4(3 + h) is −12 − 4h. With only −12 the −4h is lost, and after dividing by h that is a −4 missing from the quotient.

See the worked solution

Where it comes up

Practise against it

Each of these has an answer this slip gives. Work them on paper: if you fall into it, the verdict names it and the question comes back in review.

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