B(t) = (1-t)³P0 + 3(1-t)²tP1 + 3(1-t)t²P2 + t³P3

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B′(t) = 3(1-t)²(P1 - P0) + 6(1-t)t(P2 - P1) + 3t²(P3 - P2)

B″(t) = 6(1-t)(P2 - 2P1 + P0) + 6t(P3 - 2P2 + P1)

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B′(0) = 3(P1 - P0)

B′(1) = 3(P3 - P2)

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B″(0) = 6(P2 - 2P1 + P0)

B″(1) = 6(P3 - 2P2 + P1)

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B′(0) = (y1 - y0)/(x1 - x0)

B′(1) = (y3 - y2)/(x3 - x2)

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B″(0) = (y2 - 2y1 + y0)/(x2 - 2x1 + x0)

B″(1) = (y3 - 2y2 + y1)/(x3 - 2x2 + x1)