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Calculating the derivative of a function of the form $f(x)=ax+b$ from first principles.

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Differentiate $f(x)=\\simplify{{a}*x+b}$ from first principles.

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For a function $f(x)$, its derivative is defined as \\[\\frac{df}{dx}=\\frac{f(x+h) - f(x)}{h} \\quad\\text{in the limit as $h$ tends to $0$.}\\]

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This is written \\[ \\frac{df}{dx}= \\lim_\\limits{h\\to 0}\\frac{f(x+h) - f(x)}{h}.\\]

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So, for the function $f(x)=\\simplify{{a}*x+b}$,

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\\begin{split}\\frac{df}{dx}&=\\lim_\\limits{h\\to 0} \\frac{f(x+h)-f(x)}{h}\\\\ &=\\lim_\\limits{h\\to 0} \\frac{[ \\simplify{{a}*(x+h)} + \\var{b}] - [\\simplify{{a}*x} +\\var{b}]}{h}\\\\ &=\\lim_\\limits{h\\to 0} \\frac{\\simplify{{a}*x}+\\simplify{{a}*h}+\\var{b}-\\simplify{{a}*x}-\\var{b}}{h}\\\\ &=\\lim_\\limits{h\\to 0} \\frac{\\simplify{{a}*h}}{h}\\\\ &=\\lim_\\limits{h\\to 0} \\var{a}\\\\ &=\\var{a}\\end{split}

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x coefficient

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Constant coefficient

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$\\frac{df}{dx}= $[[0]]

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