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This is an A* level GCSE Maths question. 'Solve' means we need to find what value x represents, but in the question this x appears on the denominator (bottom half) of the fractions which we can't use. ...

First of all, "second derivative", d²y/dx², is what you get when you differentiate the first derivative (dy/dx).

The second derivative can be used as an ea...

To work out averages we add up all of the ages and divide by the number of people in the group.

So that means in the first group, before the new person joined in, all the ages added up an...

Remember the rules for differentiation?

We take each term which looks like axⁿ where a and n are just numbers and we turn it into: (an)x^n-1

So for this...

There is no need to solve the quadratic equation here. Use the formulae for the sum and product of roots where:

a+b = -b/a

and

ab = c/a

Therefore...