Math Question: How many different 4-digit numbers can be formed using the digits 1, 2, 3, and 4 without repetition?
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Question: What is the derivative of f(x) = 3x^2 + 2x - 1 with respect to x?
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What is the general equation of an ellipse centered at (h, k), with semi-major axis a, semi-minor axis b, and the foci located at (h ± c, k), where c = √(a^2 - b^2)?