View Full Version : Algebra Quesiton... :rolleyes:

ryanVickers

January 23rd, 2008, 05:16 AM

I'm usually top of the class in math but this has been bugging me...

(2(n - 5))/(3(n + 4)) = 6/7

what's n?

I don't need you to do it for me, but the process would be nice... :p (there are others like it)

saulgoode

January 23rd, 2008, 05:34 AM

Multiply both sides by (3(n + 4)). Collect your terms and solve the resulting quadratic equation.

schauerlich

January 23rd, 2008, 05:37 AM

I don't believe there will be a quadratic equation... once you distribute, it's all first power, and there's no more multiplication...

bigdidz

January 23rd, 2008, 05:41 AM

first it does equal to:

(n-5) / (n+4)= (6*3) / (2*2)

(n-5) * (2*2) = (6*3)*(n+4)

4*n-20 = 18*n+72

0 = 14*n+92

-92/14 = n

ugm6hr

January 23rd, 2008, 05:54 AM

Multiply both sides by (3(n + 4)). Collect your terms and solve the resulting quadratic equation.

I think the better method is to multiply both sides of equation by: 21(n+4)

The reason for this is if you write the equation out in full, the "bottom line" (i.e. denominators) are 3(n+4) x 7 = 21(n+4). This removes all denominators to reveal a linear equation.

Then you should arrive at a linear equation, which should be fairly straightforward (as long as you can multiply and divide).

bigdidz

January 23rd, 2008, 05:58 AM

I just forgot I is very important to know that 'n' is NOT (-4). If it would be, we would divide by 0 (zero) and In my country, we cut the head off the person how divide by zero.

ryanVickers

January 23rd, 2008, 06:00 AM

yeah, I got that much trying to run it through my program.. :rolleyes:

davarino

January 23rd, 2008, 07:09 AM

Multiply both sides of the equation by 7*3(n+4) (namely, 21n+84).

You get 14n-70 = 18n+72

which reduces to -4n = 142

which (when divided by -4 on both sides of the equation) yields n = -35.5

which is the answer.

You are very welcome. :)

macogw

January 23rd, 2008, 07:09 PM

like this...

http://ubuntuforums.org/attachment.php?attachmentid=57313&d=1201111716

ryanVickers

January 24th, 2008, 05:46 AM

yeah, I finally got that much :p

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