Saturday, August 17, 2013

A-LEVEL MATHEMATICS Topic : Asymptotes

Asymptotes are equations that describe the behaviour of a curve as one coordinate tends to infinity. For reciprocal graphs – any graph of the form – the asymptotes are the set of– values orvalues that the graph cannot take.
Ifthensince that would mean dividing by 0, andsinceThese equations can also be obtained from the formby considering the denominatorwhich may not take the value 0, soand the coefficient ofin numerator and denominator. LettinggivesIn fact ifthe equation of theasymptote is given by dividing the coefficient ofin numerator and denominator to give
Example:The equation of the x asymptote isand the equation of the asymptote is given bySketching the graph can be aiding by finding the intercepts with the axes.andThe graph is sketched below.

A-LEVEL MATHEMATICS Topic : Summing Multiples Up To a Certain Number

There are three multiples of 3 less than or equal to 10 – 3, 6 and 9. We don't have to list the multiples to find how many there are. Instead we could have divided 10 by 3 and rounded down
which rounds down ro 3.
In general, to find the number of multiples ofless than or equal tofindas a mixed fraction or decimal and round the answer down to the nearest whole number.
To find the sum of the multiples of 3 less than or equal to 100, first find how many multiples of 3 there are:
which rounds down to 33, so there are 33 multiples of 3 less than 100.
These multiples of 3 are, in ascending order, 3, 6, 9, …, 99.
This is an arithmetic sequence with first termand common differenceso we can use the formula for the sum of an arithmetic sequence,giving
In fact in general, to find the sum of the multiples of k less than or equal tofind

whereindicates the result of the divisionis rounded down to the nearest whole number.

A-LEVEL MATHEMATICS Topic : Solving Quadratic Inequalities

We may be given the curveand asked to find the set of values offor which
We can start by sketching the curve and obtain:
We can just read the solutions off here:
or We could have factorised the
expression forto obtainand solvedto obtainhence the set of values of
For the quadratic above, since the coefficient ofis 1 which is positive, we know it will be a “bum” curve,so the set of solutions forwill come in two parts,or
The curve shown above isWe are asked for example to find the set of values offor whichWe can see from the graph that there is only one set of values:We could have factorised the expression forto obtainand solvedto obtainhence we could write down the set of values of
The curve shown isWe are asked
to solveThe curve is a “breast” curve and we can read off the solutionsor
We can also factorise the expression forto obtain and solvehence finding the set of solutions just given.