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If f(x)=x3log⁡exf(x) = x^3\log_e x, Then f′′(e2)f''(e^2) is equal to

Solution

✅ Correct Option: 2

Given f(x)=x3log⁡ex=x3ln⁡xf(x) = x^3\log_e x = x^3 \ln x

Using the product rule with u=x3u = x^3 and v=ln⁡xv = \ln x:

u′=3x2u' = 3x^2

v′=1xv' = \frac{1}{x}

f′(x)=3x2⋅ln⁡x+x3⋅1xf'(x) = 3x^2 \cdot \ln x + x^3 \cdot \frac{1}{x}

f′(x)=3x2ln⁡x+x2f'(x) = 3x^2 \ln x + x^2

f′(x)=x2(3ln⁡x+1)f'(x) = x^2(3\ln x + 1)


Using the product rule with u=x2u = x^2 and v=(3ln⁡x+1)v = (3\ln x + 1):

u′=2xu' = 2x

v′=3xv' = \frac{3}{x}

f′′(x)=2x⋅(3ln⁡x+1)+x2⋅3xf''(x) = 2x \cdot (3\ln x + 1) + x^2 \cdot \frac{3}{x}

f′′(x)=2x(3ln⁡x+1)+3xf''(x) = 2x(3\ln x + 1) + 3x

f′′(x)=6xln⁡x+2x+3xf''(x) = 6x\ln x + 2x + 3x

f′′(x)=6xln⁡x+5xf''(x) = 6x\ln x + 5x

f′′(x)=x(6ln⁡x+5)f''(x) = x(6\ln x + 5)


At x=e2x = e^2:

f′′(e2)=e2(6ln⁡(e2)+5)f''(e^2) = e^2(6\ln(e^2) + 5)

Since ln⁡(e2)=2ln⁡(e)=2\ln(e^2) = 2\ln(e) = 2:

f′′(e2)=e2(6×2+5)f''(e^2) = e^2(6 \times 2 + 5)

f′′(e2)=e2(12+5)f''(e^2) = e^2(12 + 5)

f′′(e2)=17e2f''(e^2) = 17e^2

Therefore, f′′(e2)=17e2f''(e^2) = 17e^2

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