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Solve 2x+3y=7 3x+2y=4 for x and y.

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fazzy99 | Student, Grade 10 | eNotes Newbie

Posted December 9, 2011 at 5:55 PM via web

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Solve 2x+3y=7 3x+2y=4 for x and y.

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grudraprasad | Student, Grade 10 | (Level 1) eNoter

Posted December 9, 2011 at 9:34 PM (Answer #1)

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mmm it's vaary easy

2x+3y =7........equation 1

3x+2y =4............................eq.2

now, multiplying 3 with eq.1 & 2 with eq. 2 we get-

6x+9y =21

6x+4y =8

-

____________

5y       =13

or y     =13/5

now solve x using the value of y

 

 

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iwalkalone | Student, Grade 10 | eNotes Newbie

Posted December 10, 2011 at 11:49 PM (Answer #2)

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hey..!!

2 x + 3y = 7 .....(1) multiply by 3

3x + 2y = 4 ..........(2) multiply by 2

from (1)

6x + 9y = 21 ........(3)

from (2)

6x + 4y = 8 .....(4)

(3)-(4)

6x + 9y = 21

6x + 4y = 8

(-)   (-)    (-)

solve it further .. u'll get y = 13/5

nw.. from (1)

2x + 3*13/5 = 7

2x + 39/5 = 7

2x = 7/1 - 39/5

2x = -4/5

x = -4/5*2

x = -2/5

u can verify it too...!!

see.. m verifying...!!

=2*-2/5 + 3*13/5

= -4/5 + 39/5

= 35/7

=7

hence.. its right...!!

hope i helped.... :)

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted December 12, 2011 at 1:24 AM (Answer #3)

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The values of x and y have to be determined given that :

2x+3y=7...(1)

3x+2y=4...(2)

2*(2) - 3*(1)

=> 3*x*2 + 2*y*2 - 3*2*x - 3*y*3 = 4*2 - 3*7

=> 6x - 6x + 4y - 9y = 8 - 21

=> -5y = - 13

=> y = 13/5

substitute in (1)

=> 2x + 3*(13/5)=7

=> x = (7 - 39/5)/2

=> -4/10

=> -2/5

The required value of x = -2/5 and y = 13/5

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