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anonymous

  • one year ago

Let f(x) = 3x^2 – x + 2 and g(x) = 5x^2 – 1. Find f(g(x)). Please explain it to me as well! Thanks :)

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  1. welshfella
    • one year ago
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    f(g(x)) - work for the ' inside out'. g(x) replaces the x in f(x)

  2. welshfella
    • one year ago
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    |dw:1439234684746:dw|

  3. anonymous
    • one year ago
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    so, f(x) = 3x^2 – x + 2 and g(x) = 5x^2 – 1 becomes: f(x) = 3(5x^2 – 1)^2 – 5x^2 – 1 + 2

  4. welshfella
    • one year ago
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    yes you are on the way but put parentheses around the 5x^2 - 1

  5. welshfella
    • one year ago
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    - otherwise you'll get your signs wrong

  6. anonymous
    • one year ago
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    f(x) = 3(5x^2 – 1)^2 – (5x^2 – 1) + 2?

  7. welshfella
    • one year ago
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    and its f(g(x)) not f(x)

  8. welshfella
    • one year ago
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    yes

  9. anonymous
    • one year ago
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    ohhh okay okay so f(g(x)) = 3(5x^2 – 1)^2 – 5x^2 – 1 + 2

  10. welshfella
    • one year ago
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    no - you have to distribute the - over the parentheses so its -5x2 + 1

  11. anonymous
    • one year ago
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    @welshfella after this question can you please help me?

  12. welshfella
    • one year ago
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    - (5x^2 - 1) = -5x^2 + 1

  13. anonymous
    • one year ago
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    i meant to type that but i hit copy and paste and put the old equation, sorry

  14. anonymous
    • one year ago
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    f(g(x)) = 3(5x^2 – 1)^2 – 5x^2 + 1 + 2

  15. anonymous
    • one year ago
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    then do i just solve normally?

  16. welshfella
    • one year ago
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    yes but i guess they want you to expand that now 3(5x^2 - 1)^2 = 3(25x^4 -10x^2 + 1)

  17. welshfella
    • one year ago
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    then simplify 3(25x^4 -10x^2 + 1) - 5x^2 + 3 = 75x^4 - 30x^2 + 3 - 5x^2 + 3 combine like terms then thats it

  18. anonymous
    • one year ago
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    3(5x^2 - 1)^2 expand: 3(25x^4 -10x^2 + 1) simplify: 3(25x^4 -10x^2 + 1) - 5x^2 + 3 = 75x^4 - 30x^2 + 3 - 5x^2 + 3 that's all? not as hard as i thought. thank you!

  19. welshfella
    • one year ago
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    yw

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