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cbAuroraIn

  • 3 years ago

I'm trying to solve 2x^2+11x-21 by quadratic formula. Factoring gives 3/2, -7, but by the formula (which should always work), I get: (-11/4)+/-((22/4)(42)^(1/2)). Can anyone help me spot my stupid error?

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  1. lalaly
    • 3 years ago
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    are u still there?

  2. mominanisar
    • 3 years ago
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    factoring gives 3/2, -7, the quadratic formula is x=(-b±sqrt(b^2-4ac))/2a from your equation a=2,b=11,c=-21 put values in formula x=(-11±sqrt(121-(168)))/2x2 x=(-11±sqrt(289))/4 x=(-11±17)/4. x=3/2, -7

  3. jhonyy9
    • 3 years ago
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    so if factoring this is right (2x-3)(x+7)=2x2+11x-21 so than your got solutions x=3/2 and x=-7 is right,correct sure always

  4. jhonyy9
    • 3 years ago
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    mominanisar ATTENTION in this calcules are some errore because inside squarroot there not is minus 168 correct,right is plus 168 and in thgis way will get these correct factorized resultes

  5. jhonyy9
    • 3 years ago
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    check it newly please

  6. mominanisar
    • 3 years ago
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    i am seriously sorry actually this step is likex=(-11±sqrt(121-(168)))/2x2 new onex=(-11±sqrt(121-(-168)))/2x2 because 'c' is minus

  7. mominanisar
    • 3 years ago
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    it is a typing mistake by me

  8. cbAuroraIn
    • 3 years ago
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    Thanks!

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