Solving a system of linear equations using elimination with multiplication and addition

Algebra
Tutor: None Selected Time limit: 1 Day

Solve the following system of equations

-4x + 9y = -16

2x - 5y = 8

Answer

x=

y=

Nov 14th, 2015

Thank you for the opportunity to help you with your question!

x=4

y=0

method of solving

-4x + 9y = -16

2x - 5y = 8

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

-4x + 9y = -16

x  = (8+ 5y)/2

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

-4*(8+5y)/2 +9y=-16

x  = (8+ 5y)/2

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

-16-10y+9y=-16

x=(8+5y)/2

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

-16-y=-16

x  = (8+ 5y)/2

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

-y=-16+16   -> y=0

x=(8+5*0)/2 ->x=4

Let's check

-4*4 + 9*0 = -16   -16=-16

2*4 - 5*0 = 8          8=8


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Nov 14th, 2015

is it fine method? or you need to do it with elimination and multiplication method? I can do it in different ways


Nov 14th, 2015

 No you were right.  Thanks

Nov 14th, 2015

Here is method of multiplication and adding

-4x + 9y = -16

(2x - 5y = 8) * 2

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

-4x+9y=-16

4x - 10y=16

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

-4x+9y + 4x - 10y = -16 + 16 

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

y=0

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

2x - 5y = 8

y=0

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

x=4

Same as 1st method

Nov 14th, 2015

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