SOLUTION: Trying to assist 13 yr old son.. Just when I think there wont be a problem helping him cause he says it's LCD'S mom. I look at the problem and it involves fractions and LCD'S, t

Algebra ->  Equations -> SOLUTION: Trying to assist 13 yr old son.. Just when I think there wont be a problem helping him cause he says it's LCD'S mom. I look at the problem and it involves fractions and LCD'S, t      Log On


   

Question 243869: Trying to assist 13 yr old son..
Just when I think there wont be a problem helping him cause he says it's LCD'S mom. I look at the problem and it involves fractions and LCD'S, these I do not know how to do. Any help much appreciated..
1. 5/x-6,7/x^2-12x+36
2.5/7ab^5,2/7a^3b^3
Can anyone help me with these problems?

Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
1. 5/x-6,7/x^2-12x+36

I'm not sure what they want done with these.

5/(x-6) separated by a comma, and then 7/(x^2-12x+36)

Are they asking for the common denominator?

If so, you would multiply 5%2F%28x-6%29 by %28x%5E2-12x%2B36%29%2F%28x%5E2-12x%2B36%29, and you would multiply 7%2F%28x%5E2-12x%2B36%29 by %28x-6%29%2F%28x-6%29.

You would get:

%285+%2A+%28x%5E2-12x%2B36%29%29+%2F+%28%28x-6%29%2A%28x%5E2-12x%2B36%29%29 and you would get:

%287%2A%28x-6%29%29+%2F+%28%28x-6%29%2A%28x%5E2-12x%2B36%29%29

These would now have common denominators.

In general, you get a common denominator by multiplying one of the fractions by the denominator of the other fraction and vice versa.

you have a/b + c/d

multiply a/b by d/d to get ad/bd

multiply c/d by b/b to get cb/bd

now that you have common denominators, you can add them together.

you would get:

ad/bd + cb/bd = (ad+cb)/bd

To put that into number, you might start off with:

2/4 + 3/5

you would multiply 2/4 * 5/5 to get 10/20

you would multiply 3/5 by 4/4 to get 12/20

they now have common denominators.

you add 10/20 + 12/20 to get 22/20 which is your answer.

to confirm, use your calculator.

calculate 2/4 to get .5
calculate 3/5 to get .6
add them together to get 1.1

calculate 22/20 to get 1.1

they are the same.

your algebraic fractions work the same way.

------------------------

2.5/7ab^5,2/7a^3b^3

I'm assuming you need to find the common denominator again.

multiply your first equation by %287%2Aa%5E3%2Ab%5E3%29%2F%287%2Aa%5E3%2Ab%5E3%29 to get:



multiply your second equation by (7*a*b^5) / (7*a*b^5) to get:



They now have common denominators of ((7 * a * b^5) * (7 * a^3 * b^3))

If they did not ask you to simplify your equations, then you are done.

If they asked you to simplify your equations, then you have to combine like terms as well.

For example:

((7 * a * b^5) * (7 * a^3 * b^3)) can be simplifed further to be:

49%2Aa%5E4%2Ab8 because 7%2A7+=+49 and a%2Aa%5E3+=+a%5E4 and b%5E5%2Ab%5E3+=+b%5E8
Some websites that might be able to help you are:

http://www.wtamu.edu/academic/anns/mps/math/mathlab/
http://www.sosmath.com/
http://www.purplemath.com/