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Maxima and minima can be found by differentiating the function for the curve and setting the differential to zero (the value of the slope at the turning point). For example, differentiating the function for the parabola y = 2x2 - 8x gives dy/dx = 4x - 8. Setting this equal to zero gives x = 2, so that y = -8 (found by substituting x = 2 into the parabola equation). Thus the function has a minimum at the point (2, -8).