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April 18, 2015

Posted by **Melissa** on Thursday, September 22, 2011 at 11:20pm.

a) use function notation to express the final answer in terms of the orginal number

b)determine the outputs for the input numbers 1, -1, & 7

c) determine the maximum result possible

I need help with this question i am so confused!!!!

- math -
**Reiny**, Friday, September 23, 2011 at 9:10amthink of a number -- x

multiply by 5 ---> 5x

subtract that product from 20 ---> 20 - 5x

multiply that by original number --> x(20-5x)

= -5x^2 + 20x

b) just put in each of the given values

e.g. for x=7

result = -5(49) + 20(7) = -105

c) let y = -5x^2 + 20x

this is represented by a parabola which opens downwards, so the y value of the vertex is the maximim

Since you are dealing with this type of question, I assume that you have been taught how to find the vertex of a parabola.

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