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Expression value intuition

In an expression like 2x+7, the value of x can change. As the variable increases and decreases, what happens to the value of the expression?
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Expression value intuitionSee video transcript

Make sure you understand the question that Sal solved.

What happens to the value of the expression 100, minus, x as x increases?
Choose 1 answer:

Let's try some practice problems!

Question 1
  • Current
What happens to the value of the expression k, plus, 35 as k decreases?
Choose 1 answer:

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  • mr pants pink style avatar for user michaeline knower
    I don't understand how any of this works.
    (5 votes)
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    • aqualine ultimate style avatar for user Avia
      It's probably easier just to look at the equations rather than talk about it...
      When you have 2x+7, when x is 1, the answer is 9. When x goes up to 2, the answer is 11. 11 is more than 9, so as the value of x increases, the value of the expression also increases.
      But when the expression is something like 10-x, when x is 1, the answer is 9. When x is 2, the answer is 8. 8 is less than 9. So as the value of x increases, the value of the expression decreases in this case.
      Hope that helps.
      (24 votes)
  • starky ultimate style avatar for user http://facebookid.khanacademy.org/100000173937440
    there seems to be many quetions on this topic. let me clear up all your confusions. just fill in the problems above with a number like 1 and do it than fill it again with a number higher. if the answer u get is lower than the other one it decreases and if it is higher than it increases and if it is the same it is the last choice. i hope this helped u all. bye bye and feel free to ask any questions to me. i will gladly try to answer them. got it guys and girls
    (13 votes)
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  • piceratops sapling style avatar for user krivera2.2015
    I don't understand because when I was doing the math above one day I did that same kind of math and I picked increase and it was wrong then I picked decrease and it was wrong then I picked it stays the same and it was wrong I didn't understand why it didn't tell me which one was right.
    (9 votes)
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  • winston default style avatar for user Chrisean Williams
    Can any of you guys can help me with this? I am really struggling with this topic. Please help...
    (8 votes)
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    • leaf grey style avatar for user Mageborn
      What part of it do you not understand? If it's all of it, you should probably go to previous lessons, and study a bit more. If there's a particular section you don't understand, or a part where it gets confusing, then we can better help you.
      (1 vote)
  • winston baby style avatar for user gc515226
    Why does it stay the same? It would decrease because it's a division problem. How does it stay the same?
    (4 votes)
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  • blobby green style avatar for user Farhan Riaz
    Hi guys, I just wanted to understand the goal of this particular lesson...

    I am in no way trying to be cynical, but, serious

    What's the point of this?
    Do we memorise this?
    i.e.
    "When you are subtracting a variable that it is Increasing, the expression Decreases"
    "When you are dividing by a variable that decreases but still remains a whole number, the expression Increases"
    "When you are dividing an increasing variable by itself, as long as it is a whole number, regardless of the value of the Variable, the answer will always be the coefficient divided by the coefficient" - in which case the usage of the variable becomes obsolete.

    Please explain,

    Thank You
    (5 votes)
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  • blobby green style avatar for user Martin Roy
    This makes no logical sense. If k=1 then 1+35=36, If k=2 then 2+35=37. both numbers are increasing. Yet the right answer is that it decreases. The explanation isn't really an explanation but a string of numbers. How could these numbers be decreasing? The second expression of the exercise says it decreases also but yet the expression is now 30-3a. I find there's no pattern regardless if the expression is addition or subtraction.
    (3 votes)
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    • blobby green style avatar for user Sivakami Pai
      I believe you are getting confused. The question is asking what will happen to k or a when their values are changed. Number k’s value is decreasing, so the overall sum is going to get smaller. Number a is a little different though, because now we are increasing the value of the subtrahend (the number that is subtracting the minuend), so the value will decrease. The questions are a little confusing so you might need to understand what exactly the question is telling you.
      (2 votes)
  • blobby green style avatar for user Belinda Cozier-fingal
    i still don"t understand the concept. Hope someone can help me simplify it to my understanding
    (3 votes)
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  • blobby green style avatar for user ayuami0001
    it hard but not that much
    (3 votes)
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  • blobby green style avatar for user M McNeal
    The video says, and the table shows, that the last problem would stay the same, yet the system markd this response as incorrect. It says that 2(t/t) decreases. Does anyone know why?
    (3 votes)
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