Question

Equação do 2 grau

x+2y=6
2x+3y=12


x-y=15
2x-4y= -14

r+y=15
r-y=60

2r+y=10
4r+2y=20

2x+5y=39
3x-2y=11

Answer 1

A) 

x+2y=6
2x+3y=12

x=6-2y
2(6-2y)+3y=12
12-4y+3y=12
-y=12-12    (-1)
y=0

x+2y=6
x+2*0=6
x=6

B)

x-y=15
2x-4y=-14

x=15+y 
2(15+y)=-14
30+2y=-14
2y=-30-14
2y=-44
y=44/2
y= -22

x-y=15
x-22=15
x=15+22
x=37



C)

r+y=15
r-y=60

r=15-y

(15-y)-y=60
15-2y=60
-2y=60-15
-2y=45
-y=45/2
-y=22,5 (-1)
y= -22,5

r+y=15
r+(-22,5)=15
r=22,5+15
r=37,5



D)
2r+y=10
4r+2y=20

y=10-2r
4r+2(10-2r)=20
4r+20-4r=20
4r-4r=20-20
r=0

2r+y-10
2*0+y=10
y=10

E)
2x+5y=39  (-3)
3x-2y=11   (2)

-6x-15y=-117
6x-4y=22

-19y=95 (-1)
y=-5

3x-2y=11
3x-2*(-5)=11
3x-10=11
3x=11+10
x=21/3
x=7