Polynomials?

Question

I know I should know this, but it slipped my mind
When I add or subtract polynomials, how do I know which sign to use?
Example problem: (I don't know how to do the squared and cubed, so I'll just write it)
(12c squared + 3cd-5d squared) + (6cd+2d squared)
I can simplify it, until I get down to figuring out what sign to use.
please help lol

Answer 1

thats hard!

Answer 2

The answer is 12c^2 + 9cd - 3d^2

^2 = squared

just group like terms. like 3cd + 6cd = (6+3)cd or 9cd
for the d^2 term, -5d^2 + 2d^2 = (-5+2)d^2 or -3d^2

Then, to factor it out and simplify, take out the common multiple of three, making it: 3(4c^2 + 3cd - d^2)
then, factor out what's in parantheses to get your final, simplified answer: 3(4c + d)(c - d)
To find which sign to use here, it's pretty much trial and error until you've been doing it for 7 years like I have. Use the FOIL method to multiply it back out, and see if you get what you originally had. If not, try again.

Answer 3

12c^2 + 3cd - 5d^2 + 6cd + 2d^2
Collecting like terms we have
12c^2 + 9cd - 3d^2
The factorise for '3'
3(4c^2 + 3cd - d^2)
3[(4c - d)(c + d)]

Hope this helps!!!

Answer 4

(12c^2 + 3cd - 5d^2) + (6cd + 2d^2)

12c^2+ 9cd - 3d^2