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

a teacher asked her students to think of a number, multiply by 5, and subtract the product from 20 , then she asked them to multiply the resulting difference by the number they first thougt of

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 9:10am
think 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.

## Answer This Question

## Related Questions

- Math - a teacher asked her students to think of a number, multiply by 5, and ...
- math - a teacher asked her students to think of a number, multiply by 5, and ...
- Math, Please Help! - Ned divided a given number by 3 and then added 2. If he ...
- Algebra - Jill asks each of her classmates to choose a number, then multiply the...
- math - I think of a number,multiply it by 3 and add 7.i get the Same answer if I...
- 5th grade math - Which pattern can describe the numbers 2,4,10,28, and so on? A...
- Math - If you multiply a number by 3 and then add 40, the result is the same as ...
- math - What are the divisibility short cuts that help you out? Odd numbers can ...
- Algebra HELP! - A teacher instructed her class to take any number and perform a ...
- Word Problem- Algebra - 1. Multiply a number by 4, then multiply this product by...

More Related Questions