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Algebra (all content)

Course: Algebra (all content)>Unit 2

Lesson 5: Two-steps equations intro

Intro to two-step equations

Here's how we solve a two step equation. It begins with the concept of equality: what we do to one side of the equation must be done to the other. Created by Sal Khan.

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• Do the rules of order of operations also count, but then in reverse?
So first you do:
3x + 2 = 14
3x = 12
x = 4

and not:

3x + 2 = 14
x + 2 = 4 6/9
x = 2 6/9
• You can change the order of operations. Your example has a flaw. You'll need to divide the 2 also by 3 on the left side.
3x + 2 = 14
x + 2/3 = 14/3
x = 12/3
x = 4
• Cant sal just / 3 (divide by three) than x 1/3 (multipy by 1/3)?
• Yes. Dividing by three is the exact same math as multiplying by 1/3.
• My teacher usually gives my class a challenge problem every week, each is supposed to be more challenging than the last, I was wondering how to solve for f(13)
f(x)=8x+g(9)-k(10)
g(1)=5+k(3)
k(1)=10-5x
2x=8
I think I know how to solve, but I'm not sure
• he draws really good though
• Wouldn't it also work to think, 3*4=12, therefore, 3x=12 is the same thing as 3*4=12, leaving x=4?
• yes, that is basically what happens when you divide by the same number on both sides
• Does anyone see those two blocks he missed or is it just me?
And did he draw that scale? If he did props to him.
• I noticed, and yeah i agree, that scale is good
• what if the x is on both sides
• If the unknown number is present on both sides then you can replace x by a number, such as 2 or 3 on both sides
• When using the railroad track method, couldn't you just say:
3x +2 = 14
-2 = -2
3x = 12
/3 = /3
x = 4
Would that work instead of multiplying 1/3 of each side?