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jagr2713

  • one year ago

f(7)= -x2+3x-6 i got 64 but its says its wrong

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  1. freckles
    • one year ago
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    \[f(x)=-x^2+3x-6 \\ \text{ and you are asked to evaluate } f(7) ?\]

  2. freckles
    • one year ago
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    by the way -x^2 means -1*x*x

  3. freckles
    • one year ago
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    -x^2 is not the same as (-x)^2

  4. freckles
    • one year ago
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    which looks like what you did

  5. jagr2713
    • one year ago
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    oh it does 0_0 i put -7^2+3(7)-6

  6. freckles
    • one year ago
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    which is -49+21-6

  7. jagr2713
    • one year ago
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    wait for mines i got 49+21-6 = 64

  8. freckles
    • one year ago
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    as said you did (-x)^2

  9. freckles
    • one year ago
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    but the question says -x^2

  10. freckles
    • one year ago
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    -x^2 is -1*x*x not (-x)*(-x)

  11. freckles
    • one year ago
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    \[-x^2=-1 \cdot x^2 \text{ or } -1 \cdot x \cdot x \\ \text{ where as } (-x)^2 =(-x) \cdot (-x)=x \cdot x =x^2 \text{ which is what you did } \\ \text{ and } -x^2 \text{ does not equal } (-x)^2 \]

  12. jagr2713
    • one year ago
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    so can u give it to me when you first plug it in

  13. jagr2713
    • one year ago
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    so its -7^2 ?

  14. freckles
    • one year ago
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    yes not (-7)^2

  15. freckles
    • one year ago
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    the exponent is on the x not the - and the x

  16. freckles
    • one year ago
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    \[g(x)=-x^2 \\ g(7)=-7^2=-(7^2)=-(7 \cdot 7)=-(49)=-49\]

  17. jagr2713
    • one year ago
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    so thats -49?

  18. freckles
    • one year ago
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    if you had \[h(x)=(-x)^2 \\ \text{ then } h(7)=(-7)^2=(-7 \cdot -7)=49\]

  19. jagr2713
    • one year ago
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    OHOHOHOHHOHO i seeeeeee

  20. jagr2713
    • one year ago
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    so if its for example f(8) we put -8^2 so 8*8=64 and the negative sign is after so -64

  21. freckles
    • one year ago
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    yes -8^2 means -(8*8)=-(64)=-64

  22. freckles
    • one year ago
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    where as (-8)^2=(-8)*(-8)=64

  23. jagr2713
    • one year ago
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    so the answer is *34?

  24. freckles
    • one year ago
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    do you see difference between -x^2 and (-x)^2 ?

  25. jagr2713
    • one year ago
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    -34?

  26. freckles
    • one year ago
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    \[-7^2+3(7)-6 \\ -49+21-6 \\ -(49-21)-6 \\ -(28)-6 \\ -28-6 \\ -34\] yes

  27. jagr2713
    • one year ago
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    OMG your the best thanks!!!!!

  28. freckles
    • one year ago
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    np

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