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bless

  • 2 years ago

Which is equal to 3[f(2x)] for f(x) = 3x^2+3/2? a.15/2 b. 81/2 c. 9x^2+9/2 d.18x^2+9

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  1. e.mccormick
    • 2 years ago
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    What part of this is giving you trouble?

  2. bless
    • 2 years ago
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    when i try to substitute the f(x) to the 3[f(2x)] i can't get the answer

  3. e.mccormick
    • 2 years ago
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    You substitute 2x into f(x), then multiply through the whole thing by 3.

  4. e.mccormick
    • 2 years ago
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    Hmmm... and yes, if that is written right, I can see why that would not get an answer.

  5. e.mccormick
    • 2 years ago
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    Is it supposed to be \(3[f(2)]\)?? Rather than 2x?

  6. bless
    • 2 years ago
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    the answer is 108x^2 + 9/2?

  7. bless
    • 2 years ago
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    its 2x

  8. e.mccormick
    • 2 years ago
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    Yes, as written, \(108x^2 + \cfrac{9}{2}\) would be correct.

  9. Muhammad_Nauman_Umair
    • 2 years ago
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    if u want this answer then u should in question (3x)^2 instead of 3(x^2)

  10. bless
    • 2 years ago
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    well there was another option to solve this problem : if the correct answer is not in the given choices, write you answer

  11. e.mccormick
    • 2 years ago
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    Ah, yes... I see what Muhammad_Nauman_Umair is pointing out.

  12. bless
    • 2 years ago
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    thanks for your help guys @Muhammad_Nauman_Umair and @e.mccormick

  13. e.mccormick
    • 2 years ago
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    \((2x)^2=4x^2\) \(3\times 4x^2=12x^2\) \(3\times 12x^2=36x^2\) Which is what I got the first time... and when you said 108 I thought I had forgotten to multiply by 3.

  14. e.mccormick
    • 2 years ago
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    \(36x^2 + \cfrac{9}{2}\) is what it should be.

  15. Muhammad_Nauman_Umair
    • 2 years ago
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    36x^2+9/2

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