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Please solve 5,6,7,8 with step by step explanation

Please Solve 5678 With Step By Step Explanation class=

Sagot :

devishri1977

Answer:

Step-by-step explanation:

7) a - 4b -c = -20  -------------(I)

3c = -6   ------------------(II)

2a +5c = -22  ---------------(III)

3c = -6    {Divide both sides by 3}

c = -6/3

c = -2

Plugin c = -2 in equation (III)

2a + 5c = -22

2a + 5*(-2) = -22

2a - 10 = -22

 2a     =  -22 + 10

     2a = -12

       a = -12/2

       a = -6

Plugin a = -6 and c = -2 in equation (I)

a - 4b -c = -20

-6 - 4b -(-2) = -20

-6 - 4b + 2 = -20

    -4b - 4 = -20

         -4b = -20 + 4

         -4b = -16

            b = -16/4

            b= -4

8) b = 2a - 9 -----------(I)

3a - 3c = 21 -------------(II)

c = a -5b- 22

-a + 5b + c = -22 -----------(III)

Multiply equation (III) by 3 and then add to equation(II)

(III)*3  -3a + 15b + 3c = -66

(II)       3a + 0b  - 3c  = 21   {Now add}

                  15b          = -45   {Divide both sides by 15}

                             b = -45/15

                              b = -3

Plugin b = -3 in equation (I)  

b = 2a - 9

-3 = 2a - 9    {Add 9 to both sides}

-3 +9 = 2a

2a = 6     {Divide both sides by 2}

 a = 6/2

 a = 3

Plugin a = 3 in equation(II)

3a - 3c = 21

3*3 - 3c = 21

9 - 3c = 21        {subtract 9 from both sides}

   -3c = 21 - 9

    -3c = 12  {Divide both sides by 2}

       c = 12/-3

c = -4

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