Solving simultaneous equations by substitution

Now we look at solving simultaneous equations by a method of substitution. This involves re-arranging one equation to isolate a variable and then substituting this into the other equation.

[Mother_Lol]

Thank you so much for the explanation. This was a really difficult concept for me to understand. Thank u again for a great explanation 😀

[espaverse]

This method was surprisingly easier than what my teacher taught me 💀

[elieelainor]

BRO'S LAUGH STUNNED MY HEART, NEVER LEAVING MATHS SIDE AGAIN

[Freedomtospeak]

Easy solve by substitution.

Original New equation
X + 3y = 11. -4x-12y = -44
4x - 7y = 6. 4x- 7y = 6
Mult top row by -4
——————————————
- 19y= -38 Divide both sides by -19
Now y = 2.

Plug in 2 for y and ….
X+ 3(2) = 11
X + 6 = 11 -> subt 6 from both sides leaving X = 5

Plug x= 5 and y = 2 into both original equations as proof

[zainabhassan]

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[Unique_]

Exam tomorrow and i still dont know how to do them

[Nobody_Arco]

Wont y become negative 2 cause positive 44 got switched to the other side so 6 minus negative 44 equals to negative 38 so help

[ritz]

There is however a different solution to x+3y and 4x-7y.To make x the subject of the formulae of the first equation we get x=11-3y.Therefor when substituting x into the second equation we get 4(11-3y)-7y=6.After that we multiply everything in the bracket with 4.So after multiplying we get 44-12y-7y=6.We then group like terms which require transposing so after grouping like terms we get -12y-7y=6-44.After simplifying this equation we get -19y=-38.We then divide by 19 at both sides so 19y divided by 19y will answer with y.-38 divided by 19 gives us -2.So y=-2.To find x we substitute y in the first equation and therefor x+3(-2)=11.We then simplify the equation which will be x+-6=11.We then transpose the 6 to the 11 to group like terms.So then x=11+6 (The sign of the transposed value turns into the opposite sign.).So then x=17.To test if we are correct use any of the equations like x=3y=11.Simplify in the expression we get 17+3(-2)=11.However both answers are correct.

[oonot]

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[en-thetics]

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[nasraahmed]

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[rogerwatson]

Love your voice, love your explanation. Thanks so much!!

[mad_]

Thank you so much. The reason I'm only really good at sciences (including comp sci) is because I only remember to do things if I know why. I couldn't remember anything about differentiation by first principles if I didn't know what we were trying to achieve, and just as such you have explained *why* we do what we do

[fatoumattajanneh]

Thank you so much 🥰💘 this topic is very hard to understand.But now I understand

[aryankannan]

You’ve just made my life so much better

[hfwdhjs]

how is -12y-7y = positive 19? shouldnt it equal -19? But even without the negative next to the 12y it would be positive 5. or maybe 12y minus negative 7y, which does equal +19?

[abdulrahmansalaudeen]

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[syedmohammadwasi]

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[victorianameneamupolo]

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[craniax]

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