SOLUTION: Solve system by substitution x-2y=-7 8x-2y=0

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Question 1064593: Solve system by substitution
x-2y=-7
8x-2y=0
Found 2 solutions by ikleyn, MathTherapy:
Answer by ikleyn(52803)   (Show Source): You can put this solution on YOUR website!
.
Solve system by substitution
x-2y=-7
8x-2y=0
~~~~~~~~~~~~ 

 x - 2y = -7,    (1)
8x - 2y =  0.    (2)


From (1), express x = -7 + 2y and then substitute it into (2) replacing "x". You will get

8*(-7+2y) - 2y = 0,

-56 + 16y - 2y = 0,

14y = 56   ---->  y = {{56/14}}} = 4.

Can you complete the solution from this point ?


On the Substitution method, Elimination method, Determinants' method for solving the systems of two linear equations
in two unknowns see the lessons
    - Solution of the linear system of two equations in two unknowns using determinant
    - Solution of the linear system of two equations in two unknowns by the Substitution method
    - Solution of the linear system of two equations in two unknowns by the Elimination method
    - Geometric interpretation of the linear system of two equations in two unknowns
in this site.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Systems of two linear equations in two unknowns".


Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

Solve system by substitution
x-2y=-7
8x-2y=0
x - 2y = - 7_____x = 2y - 7 ----- eq (i)

8x - 2y = 0 ------- eq (ii)

Note also that eq (ii) can remain as is, or it can be REDUCED by dividing it by its GCF, 2

8(2y - 7) - 2y = 0 -------- Substituting 2y - 7 for x in eq (ii) ------ eq (ii)

16y - 56 - 2y = 0

16y - 2y = 56

14y = 56



x = 2(4) - 7 ------ Substituting 4 for y in eq (i) 



 

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