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Unit 4: Lesson 4

Topic D: Foundations

Variables, expressions, & equations

Learn what variables, expressions, and equations are. Created by Sal Khan.

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• In the example x=-2 to the power y=3 you write -2^3 that is a mistake, the right way to do it is (-2)^3 ; because the "-" sign belong to the number "2". It is no the same:
(-2)^2=4 to -2^2=-4. Thanks so much for what you are doing.
• Can I point out this is 9 YEARS ago 9 years so about 2010
• What's the difference between a variable and an expression?

Sal isn't very clear on expressions in this video. An expression is basically one or more variables (letters or symbols standing in for values) and/or constants (any of the numbers you see: 2, 0.4, -5, etc) and any operating symbols that may join them (+, -, etc). This does not include whole equations; what is on either side of the equal sign are separate expressions. In the example x + 5 = 6, x+5 is an expression and so is the constant 6, both of which evaluate to 6 since the equal
• is it possible that there is so many variables in a equation that the problem is unsolvable
• No. It would only make the problem more complex not unsolvable.
(1 vote)
• I saw the video but I still don't understand. Can someone tell the difference between expressions, equations, and inequalities in a simpler way?
• Just think about equations as anything that is giving an answer, and has A equal sign example: (2+2=4). Inequalities is comparing something if it is greater, less than, or equal too, it has one of those signs as well. example:(2/3 < a). Expressions are equations bunched together that do not have their answers, you have to find them with the information you have in the equations. An expression example: (a+4+2) = (3+3+a). and if a is 3, what will the expression be?
(1 vote)
• why does this video sound soo clear it was made 11 years ago!
• I watched the video, but I'm still having a little trouble understanding what the difference is between an expression, inequality, and equation. Can someone explain it a bit simpler for me, please?
• I really don't know either. can someone help us?
(1 vote)
• so the variable is the unknown factor of an equation
• 35-3× =10 how would I solve this expression