# Little help please - simultaneous equations

• Apr 1st 2012, 11:50 AM
tommy68
Little help please - simultaneous equations
I'm to solve simultaneous equation :

y = −3x + 2
y = 2x2 −7x−4

I know the what the answer should be but i never seem to get it, so im clearly doing it wrong! :)
Any help especially on how to solve it would really be appreciated!
• Apr 1st 2012, 12:26 PM
emakarov
Re: Little help please - simultaneous equations
Equating the right-hand sides of the two equations gives you a quadratic equation. If you have trouble solving it, please post your solution steps so that we can give you feedback.

In plain text, it is customary to write x^2 for \$\displaystyle x^2\$.
• Apr 1st 2012, 12:42 PM
tommy68
Re: Little help please - simultaneous equations
Thank's :)

Heres one of my attempts...theres been a few!

0 = 2x^2 - 4x - 6
( 2x+3)(x-2)
2x+3 + 0 and x-2 = 0
x is -1.5 and x is 2

Im supposedly to have the answer of -1 and 5 somehow, but no idea how !

Thanks for any input in advance :)
• Apr 1st 2012, 12:55 PM
emakarov
Re: Little help please - simultaneous equations
Quote:

Originally Posted by tommy68
0 = 2x^2 - 4x - 6
( 2x+3)(x-2)

(2x+3)(x-2) = 2x^2 - x - 6 ≠ 2x^2 - 4x - 6.

If you know the quadratic formula, you should use it.

Quote:

Originally Posted by tommy68
Im supposedly to have the answer of -1 and 5 somehow

The solutions are x = -1 and x = 3. The value x = 5 does not fit the original equations.
• Apr 1st 2012, 12:59 PM
tommy68
Re: Little help please - simultaneous equations
ah i see, thank you very much for the help! Seems i've not been doing it right at all! Back to the drawing board for me!