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anonymous

  • one year ago

am I right at all? Given that f(x) = 2x + 5 and g(x) = x − 7, solve for f(g(x)) when x = −3. −15 << my answer −8 10 25

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  1. Hero
    • one year ago
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    @FrostFlare23 mind showing the work you did to arrive at that answer?

  2. anonymous
    • one year ago
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    alright give me a second

  3. anonymous
    • one year ago
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    well techincally I did work but none of the answers matched mine

  4. anonymous
    • one year ago
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    f(-3) = 2(-3) + 5

  5. anonymous
    • one year ago
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    f(-3) = -6 + 5 = -1

  6. anonymous
    • one year ago
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    did I screw up?

  7. anonymous
    • one year ago
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    @Hero ?

  8. anonymous
    • one year ago
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    you there dude?

  9. Hero
    • one year ago
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    Looks right so far, but ...

  10. Hero
    • one year ago
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    You should calculate f(g(x)) first, then calculate f(g(-3)).

  11. anonymous
    • one year ago
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    oh. uhm how do I do that? thats the only thing that confuses me

  12. Hero
    • one year ago
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    I'll get you started: f(x) = 2x + 5 1. Replace x with g(x) f(g(x)) = 2(g(x)) + 5 2. Replace g(x) with x - 7 = 2(x - 7) + 5 3. Simplify the expression

  13. anonymous
    • one year ago
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    hmm... 2x -14 +5?

  14. Hero
    • one year ago
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    So f(g(x)) = 2x - 14 + 5, but that can also be further reduced, right?

  15. anonymous
    • one year ago
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    I think so

  16. Hero
    • one year ago
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    Because -14 + 5 = -9 so f(g(x)) = 2x - 9 Now calculate f(g(-3))

  17. anonymous
    • one year ago
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    hmm. so we would add 14 to both the 5 and the -14?

  18. anonymous
    • one year ago
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    oh sorry. lol late comment there

  19. Hero
    • one year ago
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    @FrostFlare23 waiting on you ...

  20. anonymous
    • one year ago
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    alright

  21. anonymous
    • one year ago
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    so we would then divide 2 to both sides to isolate the X in order to get x = 4.5?

  22. Hero
    • one year ago
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    No, you just simply evaluate f(g(x)) at x = -3 f(g(x)) = 2x - 9 f(g(-3)) = 2(-3) - 9

  23. anonymous
    • one year ago
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    oh!

  24. anonymous
    • one year ago
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    alright

  25. anonymous
    • one year ago
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    so basically it would become: 2(-3) which equals -6. then we subtract -6 from 9 to get -15?

  26. Hero
    • one year ago
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    Correct.

  27. anonymous
    • one year ago
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    ok so I was right I just ha the wrong way of doing it the first time thank you!

  28. Hero
    • one year ago
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    Both ways of doing it are correct. It's just better practice to write f(g(x)) as a single expression then evaluate it once.

  29. anonymous
    • one year ago
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    alright thank you kind sir!

  30. Hero
    • one year ago
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    The problem with doing it the way is, if someone asked you what f(g(x)) is, you wouldn't be able to tell them.

  31. anonymous
    • one year ago
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    oh ok

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