I am taking a refresher class in Algebra...its been a long time. Anyways, in this expression how (why) is the 9 considered negative?
=3x + 4y + 8x - 9y - 7

Question

I am taking a refresher class in Algebra...its been a long time. Anyways, in this expression how (why) is the 9 considered negative? 
=3x + 4y + 8x - 9y - 7

phi · Answer

this can be confusing,  but the best way to keep things straight is "don't do subtraction"

treat    8x - 9y  as  8x + -9y
add negative numbers rather than subtract.

anonymous · Answer

Great thank you for the tip. I am wanting to go back to college after 22 years and I cant remember all this! Thank you again.