Question

{4x-y=8 x+y=7
{x+y=7

Answer 1

Resposta:

S = (3,4)

$\left \{ {{4x-y=8} \atop {x+y=7}} \right. \\\\\left \{ {{4x-y=8} \atop {x=7-y}} \right. \\\\4x-y=8\\\\4(7-y)-y=8\\\\28-4y-y=8\\\\-4y-y=8 - 28\\\\-5y = -20\\\\y=\frac{20}{5}\\\\y=4 \\\\\\x= 7-y \\\\x= 7- 4\\\\x=3$