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Solve the system: 2x-y=8 x+3y=9

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talal042004 | Student, Grade 11 | (Level 1) eNoter

Posted October 13, 2010 at 12:16 AM via web

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Solve the system:

2x-y=8

x+3y=9

2 Answers | Add Yours

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hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted October 13, 2010 at 12:19 AM (Answer #1)

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2x-y = 8 ..........(1)

x + 3y = 9 ...........(2)

We will use the elimination method to solve:

Let us multiply (1) by 3 and add to (2);

==> 7x = 33

==> x= 33/7

To find y we will substitute in (1):

2x - y = 8

==> y= 2x - 8 = 2(33/7) - 8

          =(66-56)/7 = 10/7

==> y= 10/7

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neela | High School Teacher | (Level 3) Valedictorian

Posted October 13, 2010 at 12:35 AM (Answer #2)

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To solve the equations:

2x-y =8...(1)

x+3y = 9...(2)

Solution:

(1)*3+(2):

(2x-y)*3+(x+3y)= 8*3+9

6x-3y+x+3y = 33

7x = 33

x = 33/7 .

(1)-2*(2)"

2x-y -2(x+3y) = 8-2*9

-7y  = -10

y = -10/-7 = 10/7.

Threfore x = 33/7 and y = 10/7

 

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