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Simplifying Algebraic Fractions...

Hey, Ive just looked at this question on the specification for my maths exam (Which I have tomorow :/), and it says I have to know how to simplify algebraic fractions, and they give me an example.

Question:

2x36+x+23=52\frac{2x-3}{6} + \frac{x+2}{3} = \frac{5}{2}

After cross multiplying the first two fractions, I got:

6x9+6x+1218=52\frac{6x-9+6x+12}{18} = \frac{5}{2}

Simplifying to give me:

12x+318=52\frac{12x+3}{18} = \frac{5}{2}

Then I cross multiplied this, which eventually gave me:

24x=84 24x = 84
x=3.5 x = 3.5

I just wanted to know if this working was right, and would give me full marks for the question?

Thanks (:
Reply 1
*Bump
Reply 2
Unknown-User


Question:

2x36+x+23=52\frac{2x-3}{6} + \frac{x+2}{3} = \frac{5}{2}

After cross multiplying the first two fractions, I got:

6x9+6x+1218=52\frac{6x-9+6x+12}{18} = \frac{5}{2}



Right, you came about this the wrong way, initially you must cross multiply but do not forget to multiply ALL the factors in the question.

So if you start with:

2x36+x+23=52\frac{2x-3}{6} + \frac{x+2}{3} = \frac{5}{2}

you need to multiply everything by 6 first, so:

2x+3+6x+123=302 2x+3 + \frac{6x+12}{3} = \frac{30}{2}

Simplifying to give me:

Then divide 6x+12 6x+12 by 3 which gives you:
2x+4 2x+4

which gives you: 2x+3+2x+4=15 2x+3+2x+4=15

Which is 4x+7=15 4x+7 = 15
So 4x=8 4x = 8
And x=2 x=2

:smile:
yes that is correct and your working is fine
Reply 4
Mr M
yes that is correct and your working is fine


Were you referring to his or mine, as his is wrong.

If you substitute 3.5 into the equation it does not work
Reply 5
Castiel
Right, you came about this the wrong way, initially you must cross multiply but do not forget to multiply ALL the factors in the question.

So if you start with:

2x36+x+23=52\frac{2x-3}{6} + \frac{x+2}{3} = \frac{5}{2}

you need to multiply everything by 6 first, so:

2x+3+6x+123=302 2x+3 + \frac{6x+12}{3} = \frac{30}{2}

Simplifying to give me:

Then divide 6x+12 6x+12 by 3 which gives you:
2x+4 2x+4

which gives you: 2x+3+2x+4=15 2x+3+2x+4=15

Which is 4x+7=15 4x+7 = 15
So 4x=8 4x = 8
And x=2 x=2

:smile:


How did the 2x32x-3 turn into a 2x+32x+3
Reply 6
Castiel
Right, you came about this the wrong way, initially you must cross multiply but do not forget to multiply ALL the factors in the question.

So if you start with:

2x36+x+23=52\frac{2x-3}{6} + \frac{x+2}{3} = \frac{5}{2}

you need to multiply everything by 6 first, so:

2x+3+6x+123=302 2x+3 + \frac{6x+12}{3} = \frac{30}{2}

Simplifying to give me:

Then divide 6x+12 6x+12 by 3 which gives you:
2x+4 2x+4

which gives you: 2x+3+2x+4=15 2x+3+2x+4=15

Which is 4x+7=15 4x+7 = 15
So 4x=8 4x = 8
And x=2 x=2

:smile:




No, I think you've made a mistake.

If you're cross multiplying on a single side of the equation, you need to multiply everything on that side by what you want to get rid of. In the case of this question it is 66\frac{6}{6} on the left hand-side of the equation.
Reply 7
Haha, coz I copied the question down wrong :confused:

Sorry for that, you are correct.

I feel stupid now :P

Ignore me!
Reply 8
Wait, so my working is correct? =S

Lol, thanks for replies btw [=
Reply 9
Yes, you (OP), are correct.
Reply 10
Yeah, your working is fine, when I checked it on paper I wrote down the wrong question :frown:
Well i did it a completely different way, but i ended up solving it not simplifying.

2x-3 /6 + x+2 /6 = 5/2

- Multiple (x+2 /6) by two.
- Multiple 5/2 by Three
- giving;

2x-3 /6 + 2x +4 / 6 = 15 /6

- Simplify into

4x +1 / 6 = 15 / 6

- Cancel down into

4x +1 = 15
4x = 16
x = 4

amirite?
Right the original poster is correct. YearForever has identified the problem with Castiel's working.
Reply 13
Ah kl thanks everyone for the replies
Reply 14
Sorry, I have one more question which im not sure if my working is correct.

Question:

1x+32x=0\frac{1}{x} + \frac{3}{2-x} = 0

Now would my working out be correct for this question:

1(2x)+3(x)x(2x)\frac{1(2-x) + 3(x)}{x(2-x)}
Which gives me:
x+2+3xx2+2x\frac{-x+2+3x}{-x^2+2x}

Which when I move the bottom to the other side, gives me:

2x+2=x22x 2x+2 = x^2 - 2x

And so when I rearrange this, I get:

x24x2 x^2 -4x -2

And I cant factorise this :s-smilie:

So Can someone point out where I've gone wrong please. I have a feeling I messed up at the beggining :/

Thanks
Reply 15
Who says it has be factorised. Complete the square or use the equation
Reply 16
MaccyG
Who says it has be factorised. Complete the square or use the equation



Hmm true, But is my working fine?
Reply 17
Unknown-User
Sorry, I have one more question which im not sure if my working is correct.

Question:

1x+32x=0\frac{1}{x} + \frac{3}{2-x} = 0

Now would my working out be correct for this question:

1(2x)+3(x)x(2x)\frac{1(2-x) + 3(x)}{x(2-x)}
Which gives me:
x+2+3xx2+2x\frac{-x+2+3x}{-x^2+2x}

Which when I move the bottom to the other side, gives me:

2x+2=x22x 2x+2 = x^2 - 2x


And so when I rearrange this, I get:

x24x2 x^2 -4x -2

And I cant factorise this :s-smilie:

So Can someone point out where I've gone wrong please. I have a feeling I messed up at the beggining :/

Thanks


How did you move it? By multiplying if so thats wrong
Reply 18
MaccyG
How did you move it? By multiplying if so thats wrong


So I cant move it to the other side,

Do I leave the equation as it is then.

Edit: Sorry Im such an idiot lol, the question tells me to simplify it, not solve it, so by leaving it in the equation before, would I be right?

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