# Justification for removing negatives on this algebra symbol manipulation question:

• Aug 19th 2010, 07:02 PM
Dantes
Justification for removing negatives on this algebra symbol manipulation question:
Hi folks! Certainly glad this forum exists

I'm following on how to do this till the very last step where -x1 is on the left and -x2 is on the right. I don't understand why one can simply remove both negatives or why they would negate each other on opposite sides of the equation?

Here's the the question and solution:

x1 & y1 and x2 & y2 are two points on a non-vertical line. X1 does not equal x2. The slope (M) of the line is:
Multiply on both sides, and divide M on both sides to begin isolating x1.Then, by subtracting http://www.aleks.com/alekscgi/x/math...D1%3F%2Cpva%3D from both sides of the equation, we get
http://www.aleks.com/alekscgi/x/math...D1%3F%2Cpva%3D,
http://www.aleks.com/alekscgi/x/math...D1%3F%2Cpva%3D,
http://www.aleks.com/alekscgi/x/math...%3F%2Cal%7B%3D.

The 2nd to last step, both x's are negative. The last step they're positive. I'm not understanding how they remove them.
Is it because it is representing a line that crosses the negative side to the positive side?

Many thanks for any help!
• Aug 19th 2010, 07:04 PM
awkward
Multiply both sides of the equation by -1.
• Aug 19th 2010, 07:06 PM
Dantes
lol thanks,

I didn't know we were allowed to do that on lines!

I'm completely humbled. Thank you haha :D