Question

Sistema

2x+y=10(1)

x+3=15(-2)

como faz ?!

Answer 1

$\left \{ {{2x+y=10} \atop {x+3y=15}} \right.$

$x=15-3y$

$2x+y=10\\2(15-3y)+y=10\\30-6y+y=10\\30-5y=10\\-5y=10-30~(-1)\\5y=-10+30\\5y=20\\y=4$

$x=15-3y\\x=15-3.4\\x=15-12\\x=3$

$\boxed{S=\{3 :4\}}$

Answer 2

2x+y=10(1)
x+3y=15(-2)

  2x + y = 10
- 2x - 6y = - 30
   0  -5y  =  - 20

- 5y = - 20 .(-1)
5y = + 20
y = 20/5
y = 4

Calculado valor de y, agora vamos calcular valor de x.
2x+y=10
2x + 4 = 10
2x = 10 - 4
2x = 6
x = 6/2
x = 3

S[x= 3 ,  y = 4]