You take a function of x and you call it y, Take any x-nought that you care to try, You make a little change and call it delta x, The corresponding change in y is what you find nex', And then you take the quotient and now carefully Send delta x to zero, and I think you'll see That what the limit gives us, if our work all checks, Is what we call dy/dx, It's just dy/dx.
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