Substitution Method Let’s Learn in 10 minutes!
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- เผยแพร่เมื่อ 28 ก.ย. 2024
- How to solve a 2 variable linear system using the substitution method.
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Memories of Mrs. Freeman teaching Algebra 1 in 1963! She was the best.
Presenter did say multimple methods. Here is another one I learned in college. Add/Subtract the 2 equasions. so make the second equation equal to this just by rearrangement x = -y + 8 - now subtract - remember double - is same as add - you get 0 = 4y + 1 - solve to get y = -1/4 - just like presenter did. then do same sub to get x. This method becomes more important if 3 variibles and 3 equations. there you will probably do the add/subtract method on 2 of them. and then on result + third, decide add/subtract or substituion. Things get a lot more complex when more than 2 variables.
instead of a shorter explanation we got a much longer and sometimes confusing talking for a simple to solve system of equations.
I'm new to this channel and I subscribed like you asked.
my method, arrange both equations so that y is the only element of one side of the equation.
X= 3Y + 9
or
3Y=X-9
and
X+Y = 8
or
Y= 8-X
additionally
3Y=3(8-X)
= 24 -3X
take both equations and set them equal. As in, 3Y = 3Y
or
X-9 = 24-3X
4X = 33
X=33/4
using either equation between X and Y..
X+Y=8
33/4+Y=8
Y=8-(33/4)
=-1/4
VERIFY
X =3Y+9
33/4=?3(-1/4)+9
33/4=?-3/4+9
=?(-3+36)/4
=❤33/4✔️
Straight forward simple problem which should take 2 minutes to explain. You waffled on for nearly 16 minutes to maximise TH-cam advertising revenues
Is there as reason you left x as a top heavy faction (33/4) and didnt change it to 8 1/4 or even 8.25?
Y=-.25 x=33/4 put the first equation into the second then y after getting that leads to
X = 3Y + 9 and X + Y = 8
Take the second equation and subtract Y from both sides giving you X = 8 - Y
Now substitute X in the first equation so that X = 3Y + 9 becomes 8 - Y = 3Y + 9
Add Y to both sides .. and subtract 9 .. giving you -1 = 4Y Y = - 1/4
and if Y = - 1/4 X = 8 - - 1/4 X = 8 1/4
Very good John, thanks
got it. basic subs, good one, thanks.
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