Quadratic equations, not a clue

Captain Slow IRL

Is there any good online guides to understanding these, I'm looking at some exercises and I can't make head or tail to working them out.

Neodymium

http://www.khanacademy.org/math/algebra/quadtratics

TheBody

What sort of problems are you having op? Are you having problems factorising them or solving them or both?

Maybe check out this to get you started:

http://www.youtube.com/watch?v=SDe-1lGeS0U

Captain Slow IRL

I got some notes off a lecturer and couldn't understand them, I was missing the last few days so didn't get a more in-depth explanation of the notes.

Thanks for the links, I was looking at Khan academy before but must have been looking in the wrong section

TheBody

If you get stuck on any bit, lash it up here and somebody will be along to help you out.

Jan Hus

Quadratic are not majorly tricky - try the quadratic formula if you are finding it hard going.

Captain Slow IRL

What exactly is a quatratic formula? Is that the big X?

I was missing from the first week of college (due to unavoidable events) and missed out on a coupel of classes. Having 2 classes since, spending a lot of time working off the notes and doing some exercises has helped me a lot.

Thanks for all the links and replies, they've helped me a lot - I'm over 14 years out of school and this stuff was like chinese to me!

TheBody

Captain Slow IRL wrote: »

What exactly is a quatratic formula? Is that the big X?

I was missing from the first week of college (due to unavoidable events) and missed out on a coupel of classes. Having 2 classes since, spending a lot of time working off the notes and doing some exercises has helped me a lot.

Thanks for all the links and replies, they've helped me a lot - I'm over 14 years out of school and this stuff was like chinese to me!

The poster was referring to the formula for solving quadratic equations. It is useful at times but is a bit slow if it can be factored using brackets.

See here for the formula:
http://en.wikipedia.org/wiki/Quadratic_equation

Captain Slow IRL

Can someone solve this?!

5x - y + 2z = 25
3x + 2y - 3z = 16
2x - y + z = 9

TheBody

Captain Slow IRL wrote: »

Can someone solve this?!

5x - y + 2z = 25
3x + 2y - 3z = 16
2x - x + z = 9

Is that a typo in the last equation? I presume you mean 2x-y+z=9 ?

Also, are you using matrices or just simultaneous equations method to solve the system?

That's not quadratic equations, that's simultaneous / system of equations
(assuming you don't use matrices)

take a pair of equations and multiply one equation so that one of the variables cancels out with the variable in the other equation of the pair

e.g. if you have 4x + 2y + z = 10
and 5x + 2y + 3z = 4

then multiply the first equation by -1 to cancel out the Ys
so it changes to -4x - 2y - z = -10
then stick the other one underneath and add them up

- 4x - 2y - z = -10
5x + 2y + 3z= 4

that leaves you with (-4 + 5)x +(3-1)z = (-10+4)
=> x +2z = -6

do the same with a different pair of the equations, if you've used equation a and b, try using b and c to again cancel out the same variable
mix the result with the result above to solve for one variable
http://www.sparknotes.com/math/algebra2/systemsofthreeequations/section1.rhtml