1. ## Simultaneous equations

My son has come home with some simultaneous equations, can anyone solve the following?

Simultaneous Equations

Q1.. 2x + y = -1

Q2.. x + 2y = 4

please show working out, will be easier for me to understand, and follow. if possible use a word file.

Thanks

2. Originally Posted by duckegg911
My son has come home with some simultaneous equations, can anyone solve the following?

Simultaneous Equations

Q1.. 2x + y = -1

Q2.. x + 2y = 4

please show working out, will be easier for me to understand, and follow. if possible use a word file.

Thanks
System of Equations can work via substitution or elimination. Elimination is the cleanest way:

$\displaystyle 2x + y = -1$
$\displaystyle x + 2y = 4$

Multiple the 2nd equation by -2 and then add the equations together.

$\displaystyle 2x + y = -1$
$\displaystyle -2(x + 2y = 4)$
======================
$\displaystyle 2x - 2x + y - 4y = -1 - 8$

$\displaystyle -3y = -9$

$\displaystyle y=3$

Plug the value of y back into either of the equations. The first one looks easiest.

$\displaystyle 2x+3=-1$

$\displaystyle 2x=-4$

$\displaystyle x=-2$

We have now solved for the system of equations by elimination.