i need help NOW with my algebra please

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• Apr 17th 2008, 05:18 PM
helpmee
i need help NOW with my algebra please
i cant even explain what it is... heres one...

b(squared)-48

helppp
• Apr 17th 2008, 05:25 PM
EthanDavis
If you are solving for b:

b^2 - 48 = 0 (set equal to 0)
b^2 = 48 (drag 48 over)
b = 7 (take square root)

This is if you're solving for b. You didn't really tell what to solve for. But this is just what I'm guessing the question is.

Hope that helps!
Ethan
• Apr 17th 2008, 05:27 PM
helpmee
thats the thing it says nothing but that! :\ im soo frustrated. it just says b^2-48 thats all, no solve for b... & im sorry but i still dont understand.
• Apr 17th 2008, 05:32 PM
theowne
There's nothing other than b so I'd guess that's what you have to solve for. Usually when you have a question like this it would say

b+2 = 4
or b(squared)=9

There's no equal sign in your question, so EthanDavis just assumed that it was equal to zero. Then he just did the algebra steps, moved over 48 to the other side and changed sign, and then solved.

However....the square root of 48 is not 7, the square root of 49 is seven. The square root of 48 is 6.93.....
• Apr 17th 2008, 05:34 PM
EthanDavis
Wow. Silly mistake. That's why I'm better off asking the questions than answering them. ;)
• Apr 17th 2008, 05:40 PM
helpmee
my teacher says this is called factoring trinomials... & ther isnt supposed to be a sign... ;[ im sosoo lost can you exlpain please? ok, so the teacher also said something like you use FOIL and the distrubutive property & factor . i dont know.. IM SO CONFUSED ;[[
• Apr 17th 2008, 05:47 PM
theowne
Oh, you're supposed to factor it...well, that would have been helpful..

There's a step by step on using that method on this website..

Intermediate Algebra Tutorial on Factoring Trinomials

But are you sure it's not b^2-49?
• Apr 17th 2008, 05:50 PM
helpmee
yeahh its b^2-48 ok heres another one... n^2-16 ? im just as confused & i have a test on this tomorrow!(Worried)
• Apr 17th 2008, 05:58 PM
theowne
That would be (n+4)(n-4)

Just think of this form:
$ax^2+bx+c$

So in that form, your question $n^2-16$, it's like this
$(1)x^2+(0)x+(-16)$

A, b and c are just constants..x is the variable (n in your question)

You want something in this form...

( ..... )( ..... )
The first terms in each bracket need to multiply to form the first term in what you started with...so if you have n(squared)-16, you know that n times n equals n(squared), so now you have this

(n ..... )(n ..... )

And then you need to look for two numbers that multiply to form "c", but add together to form b. c is -16, and b is 0 in your example. So 4 and -4 fit the circumstances...So then you have

(n+4)(n-4)
• Apr 17th 2008, 05:58 PM
Jen
With these consider your standard form $ax^2+bx+c$
In this case where there is no "b" term you are going to end up with the form (x+some number)*(x-some number)

So in the case $n^2-16$ consider the number 16, can you take the square root and get a whole number? In this case it would be four, so you can factor it thus,

$(n+4)(n-4)$

You can test this result by foiling it back out and it should look the same.
• Apr 17th 2008, 06:10 PM
helpmee
ok im understanding this more... [: thanks. so like what about a big one like this: 27t^2+18t+9?
• Apr 17th 2008, 06:37 PM
theowne
Have you learned the quadratic formula? If you can't do it simply, then you can use the quadratic formula.

$\frac{-b \pm \sqrt{b^{2} - 4ac}}{2a}$

But you can't do that here because b^2-4ac gives you a negative value, which you can't take the square root of..

..so there's no roots for this...
• Apr 17th 2008, 06:40 PM
helpmee
;[ ?? forget it... ill just try at what i think i can do, then guess at the rest. thank you all, [it HAS helped!]
• Apr 17th 2008, 06:46 PM
Jen
Quote:

Originally Posted by helpmee
ok im understanding this more... [: thanks. so like what about a big one like this: 27t^2+18t+9?

First factor out a nine, then try to think of it as foiling backwards.

your final result should look similar to this.

$9(t \pm \mbox{ some number })(t \pm \mbox{ some number })$

I put the "some number" in there because I want you to try it yourself k.
• Apr 17th 2008, 06:51 PM
helpmee
so is it:

3t^2+2t+1?

because 27 divided by 9 is 3, and 18 divided by 9 is 2, and 9 divided by 9 is 1? so what do you do after that?
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