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leozap1

  • one year ago

*Fan & Medal* Please explain how I can do this, I want to learn it. Let f(x) = -2x + 4 and g(x) = -6x - 7. Find f(x) - g(x)

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  1. jango_IN_DTOWN
    • one year ago
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    HI... I can help you

  2. leozap1
    • one year ago
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    Okay... How do I solve this?

  3. jango_IN_DTOWN
    • one year ago
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    Hmm... you should find f(x)-g(x)=(-2x+4)-(-6x-7)=-2x+6x+4+7=4x-11

  4. jango_IN_DTOWN
    • one year ago
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    \[ax-bx=(a-b)x\]

  5. jango_IN_DTOWN
    • one year ago
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    Just using this formula we did the sum here

  6. jango_IN_DTOWN
    • one year ago
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    @leozap1 did you get it?

  7. leozap1
    • one year ago
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    I'm trying just a sec

  8. leozap1
    • one year ago
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    On this part "2x+6x+4+7" aren't we suppose to subtract? It says to find f(x) - g(x)

  9. jango_IN_DTOWN
    • one year ago
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    yeah correct

  10. jango_IN_DTOWN
    • one year ago
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    -(-6)=6

  11. leozap1
    • one year ago
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    So it would be -2x-6x-4-7?

  12. jango_IN_DTOWN
    • one year ago
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    no

  13. jango_IN_DTOWN
    • one year ago
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    wait

  14. leozap1
    • one year ago
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    Ohh so since they are already negative, it makes them positive?

  15. jango_IN_DTOWN
    • one year ago
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    the expression of f(x) will not be changed. but the expression of g(x) will be its negative.. g(x)=-6x-7 so -g(x)=-(-6x-7)=6x+7

  16. jango_IN_DTOWN
    • one year ago
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    |dw:1444742322049:dw|

  17. jango_IN_DTOWN
    • one year ago
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    @leozap1

  18. leozap1
    • one year ago
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    Oh, that makes more since. So is the answer 4x+11, or is there anything else needing to be done?

  19. jango_IN_DTOWN
    • one year ago
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    nothing more... If you want an explanation more in depth, in algebraic sense, then I can offer

  20. leozap1
    • one year ago
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    I think I get it, I'll try working out other problems now. Thank you for all the help.

  21. jango_IN_DTOWN
    • one year ago
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    ok.. remember f(x)-g(x)=f(x)+{-g(x)} where -g(x) is when the expression of g(x) is multiplied by -1

  22. leozap1
    • one year ago
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    This is one of the other problems, and I honestly have no idea about it ether. If you know how to do it I can create a new post so you will get another medal.

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  23. leozap1
    • one year ago
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    Is it suppose to be multiplication? If so I can figure it out, if not I have no idea...

  24. jango_IN_DTOWN
    • one year ago
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    HI... Are you still there?? My internet connection went down

  25. leozap1
    • one year ago
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    Yea.

  26. jango_IN_DTOWN
    • one year ago
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    No that's not multiplication. For this thing you need to know composition of mappings;. Are you familiar with this term?

  27. jango_IN_DTOWN
    • one year ago
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    @leozap1

  28. leozap1
    • one year ago
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    No, sorryy

  29. jango_IN_DTOWN
    • one year ago
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    Ok.. Here we go

  30. jango_IN_DTOWN
    • one year ago
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    fog(x)=f(g(x))

  31. leozap1
    • one year ago
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    Okay so it would be f(g(x)) = 3x-7-2x-6?

  32. jango_IN_DTOWN
    • one year ago
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    f(g(x))=f(-2x-6)=3(-2x-6)-7=-6x-18-7=-6x-25

  33. jango_IN_DTOWN
    • one year ago
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    See we are given the value of f(x).. now when you need to calculate f(g(x)) just replace x by g(x) in the expression of f(x)

  34. leozap1
    • one year ago
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    So the answer would be -49?

  35. jango_IN_DTOWN
    • one year ago
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    answer is -6x-25

  36. leozap1
    • one year ago
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    f(g(x)) = -6x-25 f(g(x)) , if x=4 or (ƒ ∘ g)(4) ------> -6(4) -25 = -45???

  37. jango_IN_DTOWN
    • one year ago
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    -49

  38. jango_IN_DTOWN
    • one year ago
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    -6(4)-25=-24-25=-49

  39. leozap1
    • one year ago
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    That's what I meant, sorry.

  40. leozap1
    • one year ago
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    Would we have to do that, or just leave it like it was?

  41. jango_IN_DTOWN
    • one year ago
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    First you need to calcuate f(g(x)) in terms of x and the plug the numeric value of x, as it is given in this problem

  42. leozap1
    • one year ago
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    So like this?

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