Question

se x+y=9 e x-y=5 entao o valor de x²-y² e?

Answer 1

x + y = 9
x - y = 5
--------------
2x //  = 14
x = 14/2 = 7 ******

7 + y = 9
y = 9 - 7
y = 2 ******

x² - y2 = ( 7)² - ( 2)² = 49 - 4 = 45 ****

Answer 2

      x+y=9
       x-y=5
 
2x = 14
 x = 14/2
 x = 7

x + y = 9
7 + y = 9
 y = 9 - 7
 y = 2
 
x² - y ² =
7² - 2² = 
49 - 4 = 45         ok