please help with simple problem

**cornman** · February 19th 2009, 06:10 PM

please show me how to solve for y

(4x+y) = (x-y)

thanks

**Rapha** · February 19th 2009, 06:24 PM

Hi

Originally Posted by cornman

please show me how to solve for y

(4x+y) = (x-y)

thanks

4x +y = x - y

calculate: -4x on both sides

4x + y - 4x = x -y - 4x

0x + y = -3x - y

y = -3x -y

calculate: add +y on both sides

y +y = -3x -y +y

2y = -3x

Now divide by 2

$\frac{2y}{2} = \frac{-3x}{2}$

$y = \frac{-3x}{2}$

Ok?

Cheers, Rapha

**cornman** · February 19th 2009, 06:28 PM

Thanks Rapha. i didnt think i could subtract terms from the parentheses. what am i missing?

**Rapha** · February 19th 2009, 06:34 PM

Originally Posted by cornman

I didnt think i could subtract terms from the parentheses. what am i missing?

Yes you can, because this is a summation, not a product. These parantheses just matter, if theres another factor like

3*(4x+y) = -17*(x-y)

In this case you can't just subtract 4x like

3*(4x+y) - 4x = 3*y

This is horribly wrong.

Not sure I didn't get your point.

Rapha