Question

Resolva o Sistema .

A) X + 4 = 4
2x + y = 5

B) X + y = 31
X - y = 5

C) X + 4y = -1
-x + 15y = 20

Answer 1

A) X + 4 = 4 ------> x=4-4=0
2x + y = 5 --------> y=5


B) X + y = 31 ----> y=31-x
X - y = 5

x-(31-x)=5
x-31+x=5
2x-31=5
2x=31+5
2x=36
x=36/2
x=18

y=31-x
y=31-18
y=13


C) X + 4y = -1 ----> x= -1-4y
-x + 15y = 20

-(-1-4y)+15y= 20
1+4y+15y=20
19y= 20-1
19y=19
y=19/19
y=1

x= -1-4y
x=-1-4
x= -5