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Nathan4102

Thu May 09, 2013 5:43 pm


Grade 10 Simple Quadratic Word Problem Question

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Since I missed most of math today, I don't really get the new word problems in the homework. Could someone show me where I go next? I've already partially solved it I think.

Q: Two numbers have a difference of 8. Find the numbers if their product is a minimum.

A: [CODE]Let x rep the first number
let 8 - x rep the second number
let y rep the product of the numbers

y = (x) (8-x)
y = (8x - x?)
y = -(x? - 8x + 16) + 16
y = -(x - 4)? + 16[/CODE]

So I've put it in vertex form, which I know he wants us to do, but I'm not sure what to do from here. A bit of help would be awesome!

Nathan


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Dreadnought

Thu May 09, 2013 5:51 pm


Re: Grade 10 Simple Quadratic Word Problem Question

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x and 8-x have a difference of eight only when x is 0 or 8


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Nathan4102

Thu May 09, 2013 6:32 pm


RE:Grade 10 Simple Quadratic Word Problem Question

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Must be x + 8 then? That would change my equation, but im still not sure where to go from there.

E: In OP, ?'s are exponent 2s.


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Dreadnought

Thu May 09, 2013 7:05 pm


Re: Grade 10 Simple Quadratic Word Problem Question

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x + 8 or x - 8 both work

Once you get a parabola find the minimum (I'm assuming you know how to do this part). Congratulations you now know for which x you attain a minimum product. Now you just need to find the other number (x + 8 or x - 8, whichever you chose).


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Nathan4102

Thu May 09, 2013 7:17 pm


RE:Grade 10 Simple Quadratic Word Problem Question

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Ohhh ok, I was overthinking it. Thanks!