ATAR Notes: Forum

VCE Stuff => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematics => Topic started by: t1ffanyk on January 18, 2013, 12:08:27 pm

Title: simultaneous equations
Post by: t1ffanyk on January 18, 2013, 12:08:27 pm: I'm having trouble with a simultaneous equation. I can't for the life of me work it out by substitution or elimination.
Does anyone know another way?

Heres the equation:
7x - 6y = 20
3x + 4y = 2
Title: Re: simultaneous equations
Post by: b^3 on January 18, 2013, 12:17:31 pm: $\begin{alignedat}{1}7x-6y & =20...[1] \\ 3x+4y & =2....[2] \\ {} [1]\times3 \\ 21x-18y & =60....[3] \\ {} [2]\times7 \\ 21x+28y & =14....[4] \\ {} [4]-[3] \\ 46y & =-46 \\ \therefore y & =-1 \\ {} [1] \\ 7x-6\left(-1\right) & =20 \\ 7x & =14 \\ \therefore x & =2 \end{alignedat} $