#1
So my little sister came from summer school today and quite frankly I feel like I should be going back also. I can't solve this.

Solve the system of equation using substitution.

y+3x=5
-2x+4y=-1

I've spent an hour and I can't get this. Someone help.
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#3
y+3x=5
-2x+4y=-1

y= 5-3x
-2x+4*(5-3x)=-1
-2x + 20 - 12x = -1
-14x = -21

x=21/14 = 3/2

y= 5-3*3/2 = 10/2 - 9/2 = 1/2


30 seconds
#4
Simultaneous Equations.
Not that hard.
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#7
x = 2
y = -1
I think that's it but don't take my word for it. I'm probably wrong anyways not that good at it.
#11
simultaneous equations. not hard, its Year 9 stuff
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#12
Quote by seljer
oh you guys are just sad


I did it right seljer!

Quote by buddha
isnt there a law against not shaving? thats somewere in our constitution. i think it goes something like a girl maybe be a freak in the sheets but no be wild down stairs is treason and for that she will be beheaded.-good old Benjamin F.

#13
Quote by seljer
y+3x=5
-2x+4y=-1

y= 5-3x
-2x+4*(5-3x)=-1
-2x + 20 - 12x = -1
-14x = -21

x=21/14 = 3/2

y= 5-3*3/2 = 10/2 - 9/2 = 1/2


30 seconds

This
#16
You have to make one equation have one variable opposite the same variable on the other equation then add the equations together, solve for the one variable, then plug it into one of the original equations and solve for the other variable.
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#17
Quote by Sad But False
ahhhhh im in year nine and dont understand it?????

You will be repeating year 9 then.
#18
Quote by DarkEra97
Multiply the top one by -4, or else multiply top by 2, bottom by 3.


thats not solving by substitution

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I think the TS will know what to do next

#19
dude,, its f*kin summer,, lay off the math equations, maye then u wont feel so retarted
DO

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#21
Quote by Giant Tool
thats not solving by substitution

Oh, I missed that part. Well substitution is even easier, so that makes it nicer for the TS.
#22
Quote by BobChicken
simultaneous equations. not hard, its Year 9 stuff

I learnt it in year 8.
#23
lol thats very basic maths you know ^^
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#24
Quote by Sad But False
ahhhhh im in year nine and dont understand it?????

Thats cos ure thick :|
there are two ways to do it but i've forgotten the second way.
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#25
...or use augmented matrix, simplify into reduced echelon form.

Row Operation 1:
3 1 5
-2 4 -1

multiply the 1st row by 1/3

1 1/3 5/3
-2 4 -1

Row Operation 2:
1 1/3 5/3
-2 4 -1

add 2 times the 1st row to the 2nd row

1 1/3 5/3
0 14/3 7/3

Row Operation 3:
1 1/3 5/3
0 14/3 7/3

multiply the 2nd row by 3/14

1 1/3 5/3
0 1 1/2

Row Operation 4:
1 1/3 5/3
0 1 1/2

add -1/3 times the 2nd row to the 1st row

1 0 3/2
0 1 1/2

first column represents x = 3/2
second column represents y = 1/2

just felt like being a nerd heheh.
#26
^^or be lazy and throw it into matlab (which probably isn't worth it for a system with 2 variables)