You can put this solution on YOUR website! write x squared + 11x + 21 = 0 in the quadratic formula
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x^2+11x+21 = 0
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Quadratic Formula:
x = [-11 +- sqrt(121-4*1*21)]/2
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x = [-11 +- sqrt(37)]/2
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x = [-11+sqrt(37)]/2 or x = [-11-sqrt(37)]/2
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Cheers,
Stan H.