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Find the derivative of $81$ using the definition. Apply the definition of the derivative: $\displaystyle f'(x)=\lim_{h\to0}\frac{f(x+h)-f(x)}{h}$. The function $f(x)$ is the function we want to differentiate, which is $81$. Substituting $f(x+h)$ and $f(x)$ on the limit, we get
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$\lim_{h\to0}\left(\frac{81-81}{h}\right)$
Learn how to solve definition of derivative problems step by step online. Find the derivative of (d^2)/(dx^2)(x^4+y^4)=81 using the definition. Find the derivative of 81 using the definition. Apply the definition of the derivative: \displaystyle f'(x)=\lim_{h\to0}\frac{f(x+h)-f(x)}{h}. The function f(x) is the function we want to differentiate, which is 81. Substituting f(x+h) and f(x) on the limit, we get. Subtract the values 81 and -81. Zero divided by anything is equal to zero. The limit of a constant is just the constant.