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Help!! On Substitution and Elimantion method! PLEASEE!?

+1 vote

My problem is 9x+4y=12
x+4y=18

asked Jan 9, 2013 in ALGEBRA 2 by angel12 Scholar

4 Answers

+2 votes

9x+4y=12-------------(1)

x+4y=18--------------(2)

subtract 4y is the  each  side

x =18 -4y

substution  the x value eqution (1)

9(18 -4y) +4y =12

162 - 36y +4y =12

 -32y =12 -162

    32 y=150

 bothside divide by  32

   y=150 /32

     =75 /16

substution  the y value eqution (2)

x+4(75 /16) =18

x +75/4 =18

subtract 75/4 is the  each  side

x =18 - 75/4

x = (72 -75)/4

x = -3/4

the values are (x , y) =( -3/4 ,75/4)

answered Jan 9, 2013 by krish Pupil
+2 votes

Elimantion method

         9x+4y=12-------------(1)

  (-)   x+4y=18--------------(2)

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

       8x  = -6

        x  = -6/8

        x = -3/4

substution  the x value eqution (2)

   -3/4 +4y = 18

addition the  -3/4 is the  each  side

            4y = 18 +3/4

            4y =(72 +3 )/4

             y =75/16

the values are (x , y) =( -3/4 ,75/16)

answered Jan 9, 2013 by krish Pupil
+2 votes

9x+4y=12-------------(1)

x+4y=18--------------(2)

subtract 4y is the  each  side

x =18 -4y

substution  the x value eqution (1)

9(18 -4y) +4y =12

162 - 36y +4y =12

 -32y =12 -162

    32 y=150

 bothside divide by  32

   y=150 /32

     =75 /16

substution  the y value eqution (2)

x+4(75 /16) =18

x +75/4 =18

subtract 75/4 is the  each  side

x =18 - 75/4

x = (72 -75)/4

x = -3/4

the values are (x , y) =( -3/4 ,75/16)

    

 

answered Jan 9, 2013 by krish Pupil
+2 votes

9x+4y=12  --------------(1)
x+4y=18  ------------------(2)

(1)-(2)⇒   9x+4y=12

        (-)        x+4y=18

           ------------------------

                9x-x+4y-4y=12-18

               8x=-6

dividedby 8 each side

               (8x/8)=(-6/8)

                     x=(-2*3)/(2*4)

                    x=-3/4

there fore x= -3/4

x value substuting in equation (2)

(2)⇒x+4y=18

     (-3/4)+4y=18

adding (3/4) in each side

  (-3/4)+4y+3/4=18+3/4

       4y=(72+3)/4                           LCM 1,4 is 4

          4y=75/4

dividedby 4 each side

         4y/4=(75/4)/4

          y=75/16

there fore x= -3/4 , y=75/16

 

answered Jan 9, 2013 by richardson Scholar

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