Question

qual é o valor de x -y, sabendo que x+y=7 e x² - y²=42 ?

Answer 1

x+y=7
x²-y²=42
x=7-y
(7-y)-y²
7²-2.7.y+y²-y²=42
49-14y=42
-14y=42-49
-14y=-7
y=-7/14
y=1/2
x=7-1/2 =>
x=14/2-1/2
x=13/2
==========================
(13/2)²-(1/2)²=42
(169/4)-1/4=42
168/4=42
13/2-1/2=12/2 = 6 /////