Verified answer

a) {2x + y = 8

...{3x - y = 7

---------------------

..5x = 15

x = 3

y = 8 - 2x

y = 8 - 6

y = 2

S = {3,2}

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b) {x + 2y = 7

...{-x + 5y = -7

----------------------

..........7y = 0

...........y = 0

x + 0 = 7

x = 7

S = {0, 7}

*********************************************

c) {-3x - 2y = -4

...{5x + 2y = 5

-----------------------

...2x = 1

x = 1/2

2y = 5 - 5x

2y = 5 - 5.1/2

y = (5/2) /2

y = 5/2 * 1/2

y = 5/4

S = {1/2 , 5/4}

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d) {5x - 3y = 1

....{3x + 3y = 2

------------------------

.....8x = 3

x = 3/8

3y = 2 - 3x

3y = 2 - 3.3/8

3y = 2 - 9/8

y = (7/8) / 3

y = 7/8 * 1/3

y = 7/24

S = {3/8 , 7/24}

Fiz tudo como prometido !

a) 2x+y=8

3x-y=7

5x=15

x=3

6+y=8

y=8-6

y=2

b) x+2y=7 Multiplica por (-1)

x-5y=7

-x+2y=7

x-5y=7

7y=7

y=1

x-5=7

x=7+5

x=12

Cansei de fazer o resto, beeijo boa sorte (:

2x+y=8

x-y=7

------------

3x=15

x=15/3

x=5

x-y=7

5-y=7

-y=7-5

-y=2

y=-2