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The equation of a curve C is (x+3)(y-4)=x^2+y^2. Find dy/dx in terms of x and y

Expand to get xy+3y-4x-12=x^2+y^2Rearrange to xy+3y-4x-12-x^2-y^2 Then you have to differentiate implicitly: use product rule on xy to get:u = x v =ydu = 1 dv = dy/dx so xy differentiates to xdy/dx + y Then ...
RR
Answered by Ravi R. • Maths tutor
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The MMR vaccine gives protection against measles, mumps and rubella. How? (4 marks)

. Vaccine contains antigens from the pathogens . This is recognised by helper T cells which activates other helper T cells and B cells . B cells undergo clonal selection and produce memory + plasma cells . P...
MV
Answered by Mohit V. • Biology tutor
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Choose whether these sentences use the subjunctive or indicative tenses.

A typical subjunctive/indicative exercise- my answers are in bold. Il est important que je [venir] ce soir, car ma soeur m'attende. vienne (subj) Je pense qu'elle [être] intelligente. est (ind) Je ne pense p...
FM
Answered by Flora M. • French tutor
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Explain why atmospheric pressure decreases with increasing altitude. (3 marks)

Firstly, pressure is created by air molecules colliding with a surface. At an increased altitude there are fewer air molecules, and therefore a larger average distance between them. This means at this higher...
EB
Answered by Emily B. • Physics tutor
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Read lines 31–42. By referring to both word choice and sentence structure, analyse how the writer creates a negative impression of adults. (4 marks) (Question taken from the 2016 Higher English past paper)

Passage"Of course, it would be naïve to suggest that all teenagers can be as accomplished as Malala. However, there is, in fact, considerable evidence that the “unfinished” brain can be pretty good at s...
MC
Answered by Morvern C. • English tutor
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