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Algebra/Simultaneous Equations and the Physical World

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Expert: - 7/16/2009


Question
Solve the following systems of equations.
1. x-y=3
2x-y=-1

Answer:
Show your work:

2. 2x+4y=10
3x-2y=-9
Answer:
Show your work:  

Answer
1. x-y=3 ==> x=y+3, now substitute that into the other equation.
.. 2(y+3)-y=-1 ==> 2y+6-y=-1 ==> y=-7, so then x=-4

Similarly for the next two...
2. 2x+4y=10 ==> x+2y=5 ==> x=5-2y, now substitute that into the other
equation. 3(5-2y)-2y=-9 ==> 15-6y-2y=-9 ==? -8y=-24 ==> y=3, so x=-1

OK?

Abe  

Algebra

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Volunteer

Abe Mantell

Expertise

Hello, I am a college professor of mathematics and regularly teach all levels from elementary mathematics through differential equations, and would be happy to assist anyone with such questions!

Experience

Over 15 years teaching at the college level.

Organizations
NCTM, NYSMATYC, AMATYC, MAA, NYSUT, AFT.

Education/Credentials
B.S. in Mathematics from Rensselaer Polytechnic Institute
M.S. (and A.B.D.) in Applied Mathematics from SUNY @ Stony Brook

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