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paulb203

Member

Registered: 2023-02-24

Posts: 321

Simplifying Algebraic Fractions

I simplified an algebraic fraction to; 4x+6/(x-3)

But the answer given was 2(2x+3)/(x-3)

They hadn't expanded 2(2x+3) to 4x+6

Did I go too far, or did they not go far enough?

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Prioritise. Persevere. No pain, no gain.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Simplifying Algebraic Fractions

They are the same but what did the question say?  Sometimes you're asked to factorise fully.  In an exam, read the question carefully to make sure of this point. If it doesn't say then either should get full marks.

Some years ago I did some A level marking for Ed-Excel. The first question asked candidates to do a certain bit of algebra (part A) and then to use the result to do something else (part B).  Other ways of doing this second part could have been used except for that crucial wording. The chief examiner told us to give no marks for part B to any candidate who didn't use part A. Along with other markers I was very unhappy about this but the chief's word is law so I did as told.

You'll be pleased to know that the standard of marking is very high. The mark scheme shows all the alternative ways that may earn marks and every bit gets working credit.  If we couldn't read a candidate's writing or had some other problem with awarding marks we had to send it on to our superviser, who also checked a sample of our marking.

I have to say, I only did it that once. It was very tedious and not how I wanted to spend my life. Useful insight though.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Simplifying Algebraic Fractions

They are the same but what did the question say?  Sometimes you're asked to factorise fully.  In an exam, read the question carefully to make sure of this point. If it doesn't say then either should get full marks.

Some years ago I did some A level marking for Ed-Excel. The first question asked candidates to do a certain bit of algebra (part A) and then to use the result to do something else (part B).  Other ways of doing this second part could have been used except for that crucial wording. The chief examiner told us to give no marks for part B to any candidate who didn't use part A. Along with other markers I was very unhappy about this but the chief's word is law so I did as told.

You'll be pleased to know that the standard of marking is very high. The mark scheme shows all the alternative ways that may earn marks and every bit gets working credit.  If we couldn't read a candidate's writing or had some other problem with awarding marks we had to send it on to our superviser, who also checked a sample of our marking.

I have to say, I only did it that once. It was very tedious and not how I wanted to spend my life. Useful insight though.

Bob

I don't understand what Paul is trying to say here.

paulb203

Member

Registered: 2023-02-24

Posts: 321

Re: Simplifying Algebraic Fractions

Thanks, Bob.

The question said;

"Simplify fully"

So which is simpler; (2x+3) /(x-3)?

or; 4x+6 / (x-3)?

---

Prioritise. Persevere. No pain, no gain.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Simplifying Algebraic Fractions

I'd write 2.(2x+3) /(x-3) . Generally, fully factorised is preferred.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob