Question

Aplicando o método de substituição, resolva o seguintes sistemas:

A)x-y=5
x+3y=9

B)3x-2y=6
x-3y=2

C)x+y=4
2x+y=7

Por favor me ajudem!!!

Answer 1

a) x-y=5
x=5-y
Substituindo na outra equação:
5-y+3y=9
-y+3y=9-5
2y=4
y=4:2
y=2

X-2=5
X=5+2
X= 7

Answer 2

a)

$\left \{ {{x-y=5} \atop {x+3y=9}} \right. \\x=5+y\\\\5+y+3y=9\\4y=9-5\\4y=4\\y=1\\\\x-1=5\\x=5=1\\x=6$

b)

$\left \{ {{3x-2y=6} \atop {x-3y=2}} \right. \\x-3y=2\\x=2+3y\\\\3(2+3y)-2y=6\\6+9y-2y=6\\7y=6-6\\y=0\\\\3x-2y=6\\3x=2(0)=6\\3x=6\\x=2$

c)

$\left \{ {{x+y=4} \atop {2x+y=7}} \right.\\2x+y=7\\y=7-2x\\\\x+7-2x=4\\-x=-3 (-1)\\x=3\\\\3+y=4\\y=4-3\\y=1$

Espero ter ajudado!