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anonymous

  • one year ago

Solve x2 − 8x − 20 = 0. x = 4, x = −5 x = −4, x = 5 x = 2, x = −10 x = −2, x = 10

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  1. anonymous
    • one year ago
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    @mathmate @Teddyiswatshecallsme

  2. welshfella
    • one year ago
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    you need to find 2 numbers whose product = -20 and whose sum = -8

  3. welshfella
    • one year ago
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    these will be the values of a and b in the factors of the expression (x + a)(x + b) = 0 you can then find the zeroes

  4. welshfella
    • one year ago
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    try factoring -10 and see if you can make -8 from 2 of the factors

  5. welshfella
    • one year ago
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    sorry thats -20 not -10

  6. anonymous
    • one year ago
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    Ok I think I understand what you mean...... ok so -10 * 2 = -20....... and then I have to find a way to make -20 equal -8....?

  7. welshfella
    • one year ago
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    you are on the right track -10 and 2 is right because -10 + 2 = -8

  8. welshfella
    • one year ago
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    so that the factors are (x - 10 )(x + 2)

  9. anonymous
    • one year ago
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    Oh wow that was suprisingly simple.....

  10. welshfella
    • one year ago
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    yea when you expand the factors the -10*x and 2*x make -8x

  11. anonymous
    • one year ago
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    Ah ok thanks man

  12. welshfella
    • one year ago
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    yw now to get the zeros you equate to 0 (x - 10)(x + 2) = 0 means that x-10 = 0 or x + 2 = 0 so the zeros are 10 and -2

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