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Derivative of a sum of log, exponential, and power terms

Let f(x)=8ln⁡(x)−3ex+x4f(x) = 8\ln(x) - 3e^x + x^4. Find f′(1)f'(1).

Hint

Differentiate term by term using the constant multiple and sum/difference rules. Recall ddx[ln⁡x]=1x\frac{d}{dx}[\ln x] = \frac{1}{x}, ddx[ex]=ex\frac{d}{dx}[e^x] = e^x, and the power rule for x4x^4. Then substitute x=1x=1.

Step-by-step solution

Apply the sum/difference and constant multiple rules to differentiate term by term: ddx[8ln⁡x]=8⋅1x=8x\frac{d}{dx}[8\ln x] = 8\cdot\frac{1}{x} = \frac{8}{x}, ddx[−3ex]=−3ex\frac{d}{dx}[-3e^x] = -3e^x, and ddx[x4]=4x3\frac{d}{dx}[x^4] = 4x^3 by the power rule. Combining these gives f′(x)=8x−3ex+4x3f'(x) = \frac{8}{x} - 3e^x + 4x^3.

Now substitute x=1x = 1: f′(1)=81−3e1+4(1)3=8−3e+4=12−3ef'(1) = \frac{8}{1} - 3e^{1} + 4(1)^3 = 8 - 3e + 4 = 12 - 3e. So the final answer is f′(1)=12−3ef'(1) = 12 - 3e.

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