Maths Edexcel

Help with solving quadratics, How to choose the correct method to get the roots

mc1996

Usually the first thing I do is see whether the quadratic can be factorised. If not then completing the square or quadratic formula. I try to put off using the quadratic formula unless I have to. Don't really like using it. But thats just me...

Reply 2

MathMad

If it doesn't factorise then use either the quadratic forumla or completing the square, if it says a specific number of significant figures then it's probably gonna be the quadratic formula, and if the question hints to give the answer in a surd form then it's likely to be done by completing the square. :biggrin:

(edited 10 years ago)

Reply 3

EXTREMEninja

It depends on the quadratic in question. If it can be factorised, then this method is probably the best. Completing the square is another method, as is the formula. If the coefficients of the x terms can be easily divided, then completing the square is a fast method. Otherwise, use the formula. Do you need me to explain each method?

Reply 4

bernard1471

Original post by EXTREMEninja

Yes please, I must explain that I have Aspergers and this causes a 'delay' in me 'grasping the concept'. My learning method is not 'Rote', ie just memory, but I must 'comprehend', and try not to 'panic'
When I look @ a Quadratic that doesn't factor easily, then I'm lost as to which method I should use. Maybe I should try the 'Discriminant' to see if it will factor at all. From a sample of Q/Ans I have looked at are as follows: 3X^10X-8 the method is axc=24, then u have got to get the factors of 24 as 12x2 and be aware that12-2=10, which can replace the coefficient of middle term. I probably wouldn't know in an exam situation how to use this convoluted process. It's not just this though, as u no the exam questions don't simply as u to factorise directly, they start with a 'compounded, tricky' Q., which u must try to understand what the various process u could apply to it in order to extract a form of answer. I maybe need to be aware of all the techniques that I could apply to a typical exam question, and try to guess what sort of answer that they might be looking for, apart from the obvious questions like 'evaluate' xxxxxx, or expand xxxxx, or minimise xxxxx etc. The Edexcel C1 & C2 text books I've got don't seem to explain techniques clearly, maybe this is part of the problem as they seem to be 'older' versions. I think that I probably will need extra tuition if the College will supply that. Thanks to u for offering to help me. Bernard 1471

Reply 5

bernard1471

Original post by MathMad

Thanks for these tips, they will be useful and save time.

Reply 6

bernard1471

Original post by MathMad

This is very useful info., Thanks

Reply 7

bernard1471

Original post by mc1996

Thanks for your tips, they will help me.

Reply 8

bernard1471

Original post by mc1996

I try this path as well, thanks

Reply 9

bernard1471

Original post by EXTREMEninja

Yes the coefficients of the X terms, that's useful, Thanks

Reply 10

bernard1471

Original post by mc1996

That's helpful, Thanks

Reply 11

bernard1471

Original post by mc1996

That's great, Thanks

Reply 12

EXTREMEninja

Original post by bernard1471

Yes the coefficients of the X terms, that's useful, Thanks

I just generally see if the quadratic can easily be factorised. If I am struggling to factorise it, then I complete the square/use the formula. I try to avoid completing the square if fractions are involved, just a habit.