Question

Se {x+2y= 12
{2x-y=-1
então no valor de xy é:

a) 8 b) 10 c) 16 d) 32 e) 64​

Answer 1

Resposta:

{x+2y= 12

{2x-y=-1

x+2y= 12

x = 12 - 2y

2x - y = -1

2(12-2y) - y = -1

24 - 4y - y = -1

-5y = -25 .(-1)

5y = 25

y = 5

x+2y= 12

x + 2 . 5 = 12

x = 12 - 10

x = 2