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    • Thread Starter

    I need help with just a few modelling type quadratics questions.

    1) y = miles per gallon x= speed of car
    y=-0.01x2 + 0.975x +16, x > 0

    a) Use the model to find two speeds at which the car has a fuel consumption of 32.5 mpg.

    b) Rewrite y in the form A-B(x-C)2
    - I have B as 0.01 and C as 48.75. However I have 16 for A and the answer booklet says it is 39?? I don't know how to get to that answer.

    2) A fertiliser company uses a model to determin how the amount of fertilser used, f kilograms per hectare, affects the grain yeild g, measures in tonnes per hectare.

    g= 6 + 0.03f - 0.00006f2

    a) One farm currently uses 20 kilograms of fertiliser per hectare. How much more feriliser would he need to use to increase his yeild grain by 1 tonne per hectare?

    3) A football stadium has 25 000 seats. The football club knows that they will sell only 10,000 tickets if each ticket costs £30. They also expect to sell 1,000 more tickets every time the price goes down by £1.

    a) The number of tickets sold, t, can be modelled by the linear equation
    where £p is the price of each ticket and M is a constant. Find the value of M.

    The total revenue, £r, can be calculated by multiplying the number of tickets sold by the price of ach ticket. This can be written as:


    b)Rearrange r into the form A-B(p-C)2 where A, B and C are constants to be found.

    c) Using your answer to part b or otherwise, work out how much the football club should charge for each ticket if they wanted to make maximum amount of profit.

    So for question one, you need to find the x values for which y=32.5
    • Thread Starter

    (Original post by M4cc4n4)
    So for question one, you need to find the x values for which y=32.5
    Thank you, Ive spotted my mistake on that question now. ahah Any ideas about part 'b' or any other questions??
    Thank you again.

    You forgot to take away the 47.75^2 on b and as it is both - they add and when -0.01 it becomez 39.765625 or something
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Updated: October 15, 2017
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