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Frederick Koh


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I can answer questions concerning calculus, complex numbers, vectors, statistics , algebra and trigonometry for the O level, A level and 1st/2nd year college math/engineering student.

Experience in the area

More than 7 years of experience helping out in various homework forums. Latest Presence is over at . You can also visit my main maths website where I have designed "question locker" vaults to store tons of fully worked math problems. A second one is currently being built. Peace.


IEEE(Institute of Electrical and Electronics Engineers )


Former straight As A level student from HCJC (aka HCI); scored distinctions in both C and Further Mathematics B Eng (Hons) From The National University Of Singapore (NUS) B Sc (Hons) From University of London External (Grad Route)

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Recent Answers from Frederick Koh

2015-07-14 winning the lottery:

The first manner of calculating the required probability which you cited is flawed. If say, each of these 6 combinations can be recycled, the probability would be computed as (1/42)^6 = 1/5489031744.

2015-05-21 Question:

The problem is a first order differential equation, and can be reduced directly by integration.    Integrating both sides wrt x:    y = - x^(-2+1)/ (-2+1) - 3 x^ (-4+1)/ (-4+1) +12x +C      =   1/x + 1/(x^3)

2014-11-24 Calculus:

Let x and y denote the lengths of the sides of the rectangle.    Then xy=400  =====> y=4000/x -------(1)    Total cost involved in enclosing rectangular region    C= 30(2x)+ 30(y) + 10 (y)     = 60x +

2014-11-23 calculus:

Let the number of units remaining vacant as a result of the rent hike be x.    Then the rental price per unit would be 500+20x    Total number of occupied units as a result of the above would be equivalent

2014-11-15 Mathematics Question:

For continuity to happen, you simply need to assert that at the point x=1, both x^2-3 and cx+2 yield the same y value.    Thus, substituting x=1 into both expressions and equating them together gives


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