home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Multimedia Algebra
/
Algebra1.iso
/
ALGEBRA1
/
CHAPTER8.4T
< prev
next >
Wrap
Text File
|
1994-02-15
|
5KB
|
178 lines
176
à 8.4ïTwo Special Cases of Systems of Equations.
äïPlease solve the following systems of equations.ïNote
that ç systems are the two special cases.
âêè2x - 3y = -6êêêèx - 3y = 7
êïSolve, -4x + 6y = 12.êê Solveï-3x + 9y = -12.
Mult. by "2".è 4x - 6y = -12êMult. by "3".è3x - 9y = 21
êêï-4x + 6y = 12êêêï-3x + 9y = -12
êêêï0 = 0êêêêè0 = 9
êêè"same line"êêêè "no solution"
éSêêêë2x - 3y = -6
êThe system of equations, -4x + 6y = 12 ,ïcan be solved by either
the Addition Method or the Substitution Method.ïWe will use the
Addition Method.ïMultiply the first equation by "2".
êêêè2(2x) - 2(3y) = 2(-6)
êêêë 4x - 6y = -12
When this equation is added to the second equation, all of the terms
cancel out.êêï4x - 6y = -12
êêêë-4x + 6y =ï12
êêêêë0 = 0
When all of the terms cancel out, it is an indication that the equations
represent the same line.ïThe solution set is every point on either
line.ïAn easy way to describe the solution set in this case is to just
say that it is the "same line".ïThe original system of equations is
called a dependent system.
è To solve the system of equations,ïx - 3y = 7è, you should
êêêêêè-3x + 9y = -12
multiply the first equation by "3".
êêêë 3(x) - 3(3y) = 3(7)
êêêêï3x - 9y = 21
When this equation is added to the second equation, a false sentence
occurs.êêêï3x - 9y = 21
êêêê -3x + 9y = -12
êêêêê 0 = 9
The resulting false sentence is a very different outcome when compared
with the previous example.ïA false sentence is an indication that there
are no solutions to the system of equations.ïThe system is called a
contradictory system, and is actually two parallel lines that do not
intersect.ïThe solution set is described by saying there is "no
solution".
1
êë Solve the system,è4x + 2y = 3
êêêêë8x + 4y = 3
êA)ïsame lineè B)ïno solutionè C)ï(1,4)è D)ïnone
ü
ë Multiply the first equation by "2" and add the resulting equation
to the second equation.ê-8x - 4y = -6
êêêêè8x + 4y = 3
êêêêêï0 = -3
This is a "contradiction" and the solution set is described by saying
the original system has "no solution".
Ç B
2
êë Solve the system,è4x - 3y = 6
êêêêè -4x + 3y = -6
êA)ïsame lineè B)ïno solutionè C)ï(0,2)è D)ïnone
ü
ëAdd the two equations together just as they are.
êêêêï4x - 3y = 6
êêêê -4x + 3y = -6
êêêêê 0 = 0
This is an "identity" and the solution set of the original system is
described by saying that the two equations are of the "same line".
ÇïA
3
êë Solve the system,è2x + y = 4
êêêêè -6x - 3y = -12
êA)ïsame lineè B)ïno solutionè C)ï(1,-2)è D)ïnone
ü
ëMultiply the first equation by "3" and add the resulting equation
to the second equation.ê6x + 3y = 12
êêêê -6x - 3y = -12
êêêêê 0 = 0
This is an "identity" and the solution set of the original system is
described by saying that the two equations are of the "same line".
ÇïA
4
êë Solve the system,ï-3x + 4y = 7
êêêêë6x - 8y = 7
êA)ïsame lineè B)ïno solutionè C)ï(-1,1)è D)ïnone
ü
ë Multiply the first equation by "2" and add the resulting equation
to the second equation.ê-6x + 8y = 14
êêêêè6x - 8y = 7
êêêêêï0 = 21
This is a "contradiction" and the solution set is described by saying
the original system has "no solution".
Ç B
5
êë Solve the system,è3x + 2y = 6
êêêêè -3x - y = 0
êA)ïsame lineè B)ïno solutionè C)ï(-2,6)è D)ïnone
ü
êAddthe two equations together just as they are.
êêêêë3x + 2y = 6
êêêêè -3x - y = 0
êêêêêèy = 6
Substitute the "6" in for y in the first equation and solve for x.
êêêêë3x + 2(6) = 6
êêêêë3x + 12 = 6
êêêêêï3x = -6
êêêêêèx = -2
The solution to this system of equations is the ordered pair, (-2,6).
This system is called a conditional system.
Ç C
6
êë Solve the system,è x - 5y = -4
êêêêè -2x + 10y = 8
êA)ïsame lineè B)ïno solutionè C)ï(1,1)è D)ïnone
ü
ëMultiply the first equation by "2" and add the resulting equation
to the second equation.ê2x - 10y = -8
êêêê -2x + 10y = 8
êêêêê 0 = 0
This is an "identity" and the solution set of the original system is
described by saying that the two equations are of the "same line".
ÇïA
7
êë Solve the system,è2y = 3x - 6
êêêêè -4y = -6x + 10
êA)ïsame lineè B)ïno solutionè C)ï(2,0)è D)ïnone
ü
ë Multiply the first equation by "2" and add the resulting equation
to the second equation.ê 4y = 6x - 12
êêêêï-4y = -6x + 10
êêêêêï0 = -2
This is a "contradiction" and the solution set is described by saying
the original system has "no solution".
Ç B
8
êë Solve the system,è6x + 4y = -4
êêêêë9x + 6y = -6
êA)ïsame lineè B)ïno solutionè C)ï(1/3,1/4)è D)ïnone
ü
ëMultiply the second equation by "-2/3" and add the resulting
equations.êêè6x + 4y = -4
êêêë -6x - 4y = 4
êêêêë 0 = 0
This is an "identity" and the solution set of the original system is
described by saying that the two equations are of the "same line".
ÇïA