Math Is Fun Forum

Slowlrnr

Member

Registered: 2010-01-26

Posts: 14

Need help solving two problems

problem # 1

x+4*square root of x=5

________
problem # 2

The profit, p(x), earned by producing and selling x units is measured by the function
p(x)= -.05x^2 + 40x - 3 , where P(x) is measured in dollars.

a) Evaluate P(3) and explain what the input and output represent.

I answered 3 units sold for $112.50 profit?

b) Determine the profit that will be earned if 10 units are produced and sold.

I answered $347.00  ?

c) determine the number of units needed to be produced and sold to earn a profit of $797

I am stuck on this one.  I think I am setting up the formula wrong.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need help solving two problems

Hi Slowlrnr;

I am not sure what you want to do with this:

x+4*square root of x=5

If you want to solve this and this is what you mean;

For 2)

a) is correct.

b) is correct

c) set your function equal to 797 and solve for x. Start by clearing the fractions:

multiply by 2:

Can you do the rest?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Slowlrnr

Member

Registered: 2010-01-26

Posts: 14

Re: Need help solving two problems

The way you expressed problem one is correct

Slowlrnr

Member

Registered: 2010-01-26

Posts: 14

Re: Need help solving two problems

Problem 2 :

So after you get x^2+80x+1555=0

then what?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need help solving two problems

Hi;

Please be careful, that is not the problem. You must watch out for errors when you copy something. This is the problem.

Try to factor that. Remember, book (school) problems always have easy answers. Many teachers are lazy, the rest are motivated by a desire to see their students pass (not knocking teachers, that's just the way it is). Therefore there will almost always be a nice, easy solution. Look for it for a couple of minutes. If you can't get it then I will show it to you. Okay?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

ZHero

Real Member

Registered: 2008-06-08

Posts: 1,889

Re: Need help solving two problems

>>multiply by 2:<<

you need to multiply by 20    . . .    not by 2.

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If two or more thoughts intersect, there has to be a point!

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need help solving two problems

Hi;

Yes, ZHero is right.This is the profit function: Sorry, thought it looked like .5

Before we get to c,, your a) and b) are now wrong.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.