Questions on Algebra: Systems of Linear Equations answered by real tutors!

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Question 168738: 1.
3x=-5-x
2x+y=-5
2.
3x-5y=7
2x-y=-7
3.
x-3y=1
3x-5y=-5
: 1.
3x=-5-x
2x+y=-5
2.
3x-5y=7
2x-y=-7
3.
x-3y=1
3x-5y=-5

Answer by jim_thompson5910(9911) About Me  (Show Source):
You can put this solution on YOUR website!
# 1
Your first equation has two "x" variables. Is there a "y" term in the first equation?




# 2


Start with the given system of equations:
system(3x-5y=7,2x-y=-7)


-5(2x-y)=-5(-7) Multiply the both sides of the second equation by -5.


-10x+5y=35 Distribute and multiply.


So we have the new system of equations:
system(3x-5y=7,-10x+5y=35)


Now add the equations together. You can do this by simply adding the two left sides and the two right sides separately like this:


(3x-5y)+(-10x+5y)=(7)+(35)


(3x+-10x)+(-5y+5y)=7+35 Group like terms.


-7x+0y=42 Combine like terms. Notice how the y terms cancel out.


-7x=42 Simplify.


x=(42)/(-7) Divide both sides by -7 to isolate x.


x=-6 Reduce.


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


3x-5y=7 Now go back to the first equation.


3(-6)-5y=7 Plug in x=-6.


-18-5y=7 Multiply.


-5y=7+18 Add 18 to both sides.


-5y=25 Combine like terms on the right side.


y=(25)/(-5) Divide both sides by -5 to isolate y.


y=-5 Reduce.


So our answer is x=-6 and y=-5.


Which form the ordered pair .


This means that the system is consistent and independent.


Notice when we graph the equations, we see that they intersect at . So this visually verifies our answer.


drawing(500,500,-16,4,-15,5,<BR>
grid(1),<BR>
graph(500,500,-16,4,-15,5,(7-3x)/(-5),(-7-2x)/(-1)),<BR>
circle(-6,-5,0.05),<BR>
circle(-6,-5,0.08),<BR>
circle(-6,-5,0.10)<BR>
) Graph of 3x-5y=7 (red) and 2x-y=-7 (green)





# 3



Start with the given system of equations:
system(x-3y=1,3x-5y=-5)


-3(x-3y)=-3(1) Multiply the both sides of the first equation by -3.


-3x+9y=-3 Distribute and multiply.


So we have the new system of equations:
system(-3x+9y=-3,3x-5y=-5)


Now add the equations together. You can do this by simply adding the two left sides and the two right sides separately like this:


(-3x+9y)+(3x-5y)=(-3)+(-5)


(-3x+3x)+(9y+-5y)=-3+-5 Group like terms.


0x+4y=-8 Combine like terms. Notice how the x terms cancel out.


4y=-8 Simplify.


y=(-8)/(4) Divide both sides by 4 to isolate y.


y=-2 Reduce.


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


-3x+9y=-3 Now go back to the first equation.


-3x+9(-2)=-3 Plug in y=-2.


-3x-18=-3 Multiply.


-3x=-3+18 Add 18 to both sides.


-3x=15 Combine like terms on the right side.


x=(15)/(-3) Divide both sides by -3 to isolate x.


x=-5 Reduce.


So our answer is x=-5 and y=-2.


Which form the ordered pair .


This means that the system is consistent and independent.


Notice when we graph the equations, we see that they intersect at . So this visually verifies our answer.


drawing(500,500,-15,5,-12,8,<BR>
grid(1),<BR>
graph(500,500,-15,5,-12,8,(1-x)/(-3),(-5-3x)/(-5)),<BR>
circle(-5,-2,0.05),<BR>
circle(-5,-2,0.08),<BR>
circle(-5,-2,0.10)<BR>
) Graph of x-3y=1 (red) and 3x-5y=-5 (green)