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anonymous

  • one year ago

Solve: 16x2 − 81 = 0. x = 4, 9 x = −4, −9 x = 9 over 4, x = −9 over 4 x = 81 over 16, x = −81 over 16

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  1. anonymous
    • one year ago
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    @welshfella

  2. welshfella
    • one year ago
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    note that 16x^2 and 81 are 2 perfect squares so what are the factors of 16x^2 - 81?

  3. welshfella
    • one year ago
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    this is the difference of 2 squares a^2 - b^2 = (a + b)(a - b)

  4. anonymous
    • one year ago
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    I do believe the answer is D.

  5. welshfella
    • one year ago
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    try to factor the expression compare 16x^2 - 81 with a^2 - b^2 and plug the values in

  6. anonymous
    • one year ago
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    16^12-81^2?

  7. welshfella
    • one year ago
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    what are the square roots of 16x^2 and 81?

  8. welshfella
    • one year ago
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    no a and b are the square roots of 16x^2 and 81

  9. anonymous
    • one year ago
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    I think the answer is D. Am i correct?

  10. welshfella
    • one year ago
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    no

  11. welshfella
    • one year ago
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    what number multiplied by itself = 81?

  12. anonymous
    • one year ago
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    The answer I belive it is @welshfella make sure I am correct on this lol. B.

  13. anonymous
    • one year ago
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    @welshfella is she correct?

  14. welshfella
    • one year ago
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    no its not d the important thing is you learn how to solve this

  15. anonymous
    • one year ago
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    ok

  16. welshfella
    • one year ago
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    ok lets do it another way 16x^2 - 81 = 0 add 81 to both sides 16x^2 = 81 now divide both sides by 16 what do you get?

  17. anonymous
    • one year ago
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    I am confused.

  18. welshfella
    • one year ago
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    |dw:1439660364573:dw|

  19. anonymous
    • one year ago
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    \[\sqrt{81/16}\]

  20. welshfella
    • one year ago
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    now all you need do is find the 2 square roots of 16/81 - dont forget therea-s a positive and a negative square root

  21. welshfella
    • one year ago
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    now what is the square root of 81 and 16 ?

  22. anonymous
    • one year ago
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    Um 2.25

  23. welshfella
    • one year ago
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    2.25 is one square root but what is the other?

  24. anonymous
    • one year ago
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    -2.25

  25. welshfella
    • one year ago
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    2.225 is square root of 81/16

  26. welshfella
    • one year ago
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    yes but they want the results as a fraction what are they as fractions?

  27. welshfella
    • one year ago
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    * 2.25 i meant

  28. welshfella
    • one year ago
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    |dw:1439660690023:dw|

  29. welshfella
    • one year ago
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    really - she has left!!

  30. anonymous
    • one year ago
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    Sorry my internet went out :/

  31. anonymous
    • one year ago
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    @welshfella

  32. welshfella
    • one year ago
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    ok so what are the square roots of 81 and 16 ?

  33. anonymous
    • one year ago
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    9/4?

  34. anonymous
    • one year ago
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    yes correct :]

  35. welshfella
    • one year ago
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    also -9/4

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