You are Here: Home

# Will Math HL accept Cramer's Rule to solve a problem? Watch

1. Hey, there are a bunch of questions on linear systems of equations where you have to find a variable that makes the system have infinite solutions/no solutions/one solution.

Usually, I use Cramer's rule instead of Row reduction to solve these quickly without silly mistakes. This used to be accepted in the markschemes from a few years ago.

Now, they don't mention it. Would it still be OK to use it?
2. I'm not familiar with the terminology of the various methods, and I'm pretty sure I don't do row reduction or whatever unless I'm trying to find a general solution.

Can you not just find the determinant and set that equal to 0? When the variable is in both the system and the equation (i.e. 2kx + 3y + z = 3k being the first row) I divide throughout by the variable to ensure that the 3 (or however many) equivalences, or whatever you call it, is an actual number, then I just find the determinant and set that to 0.

I've always received full marks. What exactly is Cramer's Method?
3. (Original post by arra)
I'm not familiar with the terminology of the various methods, and I'm pretty sure I don't do row reduction or whatever unless I'm trying to find a general solution.

Can you not just find the determinant and set that equal to 0? When the variable is in both the system and the equation (i.e. 2kx + 3y + z = 3k being the first row) I divide throughout by the variable to ensure that the 3 (or however many) equivalences, or whatever you call it, is an actual number, then I just find the determinant and set that to 0.

I've always received full marks. What exactly is Cramer's Method?
Yep, that's Cramer's method lol.

So if you've been getting full marks, that method should be acceptable. Its puzzling why they've stopped using that method in the markschemes. When did you do your Math exam?
4. Well, the last time I remember doing this was for my Mock (I'm sitting the real one tomorrow) and it was a system of equations with whatever you said. November 2011 paper 1, I believe.

My teacher has always given me full marks, and she grades very strictly by the MS, but I haven't taken a look recently.

To be safe, after using the determinant why don't you just say because the determinant is 0 the inverse can't exist and hence no unique solution exists blah blah blah?
5. In similar vein, I always use synthetic division for function problem involving finding algebraic factors etc. But I always see remainder theorem on the MS..

Any suggestions?

Updated: May 2, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Stuck for things to do this summer?

Come and get some inspiration.

### Accidentally received rude picture...

Poll
Applying to university

### Your perfect course is here

Let our match making tool match you up with your ideal uni

## Make your revision easier

Don't miss out on a place at uni - get clearing email alertsStudy Help rules and posting guidelines

## Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.