Question

A=2x+5y+1,B=3y-7x-8 e C= 12x-y calcule:
A) A+B+C
B)A-B-C
C)B-A+C
D)C-A-B

Answer 1

a)

A+B+C = 2x+5y+1+3y-7x-8+12x-y = 2x-7x+12x+5y+3y-y+1-8 
A+B+C = 7x+7y-7 = 7(x+y-1)

b)

A-B-C = 2x+5y+1-(3y-7x-8)-(12x-y) = 2x+5y+1-3y+7x+8-12x+y
A-B-C = 2x+7x-12x+5y-3y+y+1+8 = -3x+3y+9 = -3(x-y-3)

c)

B-A+C = 3y-7x-8-(2x+5y+1)+12x-y = 3y-y-7x+12x-8-(2x+5y+1)
B-A+C = 2y+5x-8-2x-5y-1 = 2y-5y+5x-2x-8-1 = -3y+3x-9
B-A+C = 3x-3y-9 = 3(x-y-3)

d)

C-A-B = 12x-y-(2x+5y+1)-(3y-7x-8) = 12x-y-2x-5y-1-3y+7x+8
C-A-B = 12x-2x+7x-y-5y-3y-1+8 = 17x-9y+7