Math CentralQuandaries & Queries


Question from itsel, a student:

Find the discriminant and use it to determine the use the quadratic formula to solve the equation -2x^2+3x+2=0

Hi Itsel,

You can find the quadratic formula in Steve's response to a question from Stuart a few years ago. Stuart's quadratic was $3x^2 -5x - 4 = 0.$ The discriminant is the piece of the quadratic formula under the root sign, that it it is $b^2 - 4 a c.$ Thus for Stuart's quadratic the discriminant is

\[b^2 - 4 a c = (-5)^2 - 4 \times 3 \times (-4) = 25 + 48 = 73.\]



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