Respostas

2014-04-13T23:07:25-03:00
A)A+B-2.C
5x²+7xy+2x²-6y-2.(-9xy-3y²)
5x²+7xy+2x²-6y²+18xy+6y²
5x²+2x²-6y²+6y²+7xy+18xy
    7x² +25xy


b)2.A-B-C
2.(5x²+7xy)-(2x²-6y²)-(-9xy-3y)
10x²+14xy-2x²+12y²+9xy+3y²
10x²-2x²+12y²+3y²+14xy+9xy
     8x²+15y²+23xy


Espero ter colaborado.