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Solve the linear system equations using substitution and elimination and graph? 4x-y=5     4x+4y=-4     

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flbyrne eNotes educator | Certified Educator

calendarEducator since 2013

write151 answers

starTop subjects are Math, Science, and Arts

Solve the system of equations:

`4x-y=5 .....(1)`

`4x+4y=-4` .....(2)

To solve by substitution, rewrite (1) to determine the value of y in terms of x.

`y=4x-5....(3)`

Substitute (3) for y in (2).

`4x+4(4x-5)=-4`

`4x+16x-20=-4`

`20x=16`

`x=0.8`

Substitute x=0.8 in (3)

`y=(4)(0.8)-5=-1.8`

Thus x=0.8 and y=-1.8

To solve by elimination, subtract (2) from (1).

`4x-y=5`

`-4x-4y=4`

` ` ------------------

`-5y=9`

`y=-9/5`

`y=-1.8`

Replace y in (1) and solve for x.

`4x-(-1.8)=5`

`4x=5-1.8`

`x=3.2/4=0.8`

Thus x=0.8 and y=-1.8

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