Solve by elimination

+2 votes
Solve by elimination:
2x-y=8 and y=5x+3

X-2y=3 and 5x + 3y= 4

Y=4x-7 and 6x+3y= 19
asked Jan 2, 2013

3 Answers

+4 votes

1 ) 2x - y = 8 and y = 5x + 3

Let 2x - y = 8 ------------>(1) and

-5x + y = 3 -------------->(2)

From (1) + (2)

2x - y = 8

-5x + y = 3

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

- 3x  + 0 = 11

x  = - 11/3

Multiply 5(1) and 2(2)

5(2x - y = 8) and 2(-5x + y = 3)

10x - 5y = 40 --------------->(3) and

- 10x + 2y = 6 -------------------->(4)

From (3) + (4)

10x - 5y = 40

- 10x + 2y = 6

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

0 - 3y = 46

y = - 46/3

answered Jan 2, 2013
+4 votes

1) x - 2y = 3 and 5x + 3y= 4

Let x - 2y = 3 ---------> (1) and

5x + 3y= 4 -----------> (2)

Multiply 5 × (1)

5x - 10y = 15 ------------->(3)

From (2) and (3)

5x + 3y =  4

5x  -10y = 15

( - )

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

0 + 13y = -11

y = -11/13

Multiply 3(1) and 2(2)

3 x - 6y = 9 ---------->(4)

10x + 6y= 8 --------------->(5)

From (4) and (5)

3 x - 6y = 9

10x + 6y = 8

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

13x + 0 = 17

x = 17/13

answered Jan 2, 2013
+3 votes

3 ) y = 4x - 7 and 6x + 3y = 19

Let y = 4x - 7 ------------->(1)

6x + 3y = 19 ------------->(2)

Multiply 6(1) and 4 (2)

- 24x + 6y = - 42

24x + 12y =  76

_____________________

0 + 18y = 34

y  = 17/9

Multiply  3(1) and  1(2)

-12x + 3y = - 21

6x + 3y = 19

( - )

___________________

-18x + 0 =  - 40

x = 20/9

answered Jan 2, 2013