GMAT Math Prep - Algebra - Solving Simultaneous Equations Using Substitution by Knewton

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GMAT Math Prep

There are four steps to solving simultaneous equations using substitution.

1. Solve either equation for one variable in terms of the other.
2. Substitute this solution into the unused equation.
3. Solve for the value of the second variable.
4. Substitute to solve for the first variable.

Look at this example: 3x + y = 9 and 5x -- 2y = 4.

Step 1. Solve the first equation for y in terms of x. This would mean moving the 3x to the right of the equation so you now have y = 9 -- 3x.

Step 2. Substitute 9 -- 3x for y in the second equation. Now you will have 5x -- 2(9 -- 3x) = 4.

Step 3. When you solve for the value of the second variable, x, by expanding 2(9 -- 3x), you will have 5x -- 18 + 6x = 4. Adding the x terms gives you 11x = 22 and solving for x will give you x = 2.

Step 4. Plug x = 2 into the first equation to solve for the other variable, y. y = 9 -- 3(2) and expanding will give you y = 9 -- 6 = 3.

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[wewewahid]

fuck algebra

[Thersch]

Good job!

[lumpypinecone]

Fantastic video! it makes things all the more clearer. Thank-you ever so much.

[osomeozzy247]

how did you get 11*= 22

[TutorSAT]

Just buy the Sugnalling Word Cheat sheet by superfoiling.co m

[beckett910]

well explained but still too fast to sink in good.

[adigupta19]

Nice little explanation, nice concept, easy though