Question

eu preciso da 9 e da 10

Answer 1

9)
(x-y)² - (x+y)² = 
x²-2xy+y² - (x²+2xy+y²) = 
x²-2xy+y² -x²-2xy-y² = 
x²-x²-2xy-2xy+y²-y² = 
-4xy
10)
3x+y = 1 .(-2)
2x+2y = 1

-6x-2y = -2
2x+2y = 1
---------------
-4y = -1 .(-1)
4y = 1 --> y = 1/4

2x+2y = 1
2x+2.1/4 = 1
2x+2/4 = 1
2x+1/2 = 1
4x+1 = 2
4x = 2-1
4x = 1
x = 1/4