|Issue 1291:||wrongly drawn graph in "introduction to the quadratic equation"|
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http://www.khanacademy.org/video/introduction-to-the-quadratic-equation at ca 1:40 f(x)=x^2-x-6 results is a parabola whose minimum is at (0.5,-25/4), rather than centered around the f(x) axis as shown in the video. The commentary indeed brings up that the roots are -2 and 3, but the connection to the location of the global minimum isn't made. Further, the tip is not at -6 as claimed/drawn in the video, but at -25/4. The wrong conclusion on the location of the tip in the video is reached by assuming the minimum is at x=0 rather than the actual x=0.5: "I know it goes through -6 because when x is 0, f(x) is -6".
Sep 7, 2010
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Sep 8, 2010
Similar mistakes were made in the video http://www.khanacademy.org/video/quadratic-inequalities--visual-explanation
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