Question

Calcule as seguintes equações:
a)x-y=1 b)2x+y=0
x+2y=22 5x-2y=45

c)x+7y=200 d)x+2y=-3
x-11y=2 3x-y= -25/2

Answer 1

a)
x-y=1
x+2y=22

x=1+y

x+2y=22
(1+y)+2y=22
1+y+2y=22
3y=22-1
3y=21
y=21/3
y=7

x-y=1
x-(7)=1
x-7=1
x=1+7
x=8

b)
2x+y=0
5x-2y=45

y=-2x

5x-2y=45
5x-2(-2x)=45
5x+4x=45
9x=45
x=45/9
x=5

y=-2x
y=-2(5)
y=-10

c)
x+7y=200
x-11y=2

x=2+11y

x+7y=200

(2+11y)+7y=200
2+11y+7y=200
18y=200-2
18y=198
y=198/18
y=11

x=2+11y
x=2+11(11)
x=2+121
x=123

d)
x+2y=-3
3x-y=-25/2

x=-3-2y

3x-y=-25/2
3(-3-2y)-y=-25/2
-9-6y-y=-25/2
-7y-9=-25/2
2(-7y-9)=-25
-14y-18=-25
-14y=-25+18
-14y=-7 (-1)
14y=7
y=7/14
y=1/2
y=0,5

x=-3-2y
x=-3-2(0,5)
x=-3-1
x=-4