find the derivative of:
f(x) = 3^(x^2 + 1/x) + x^3
The derivative of the second term x³ is trivial:
d[x³]/dx = 3x²
One must use logarithmic differentiation on the first term:
let y = 3^(x² + 1/x) then ln(y) = (x² + 1/x)ln(3)
Differentiating both sides:
(1/y)dy/dx = (2x - 1/x²)ln(3)
Multiply both sides by y:
dy/dx = (2x - 1/x²)ln(3)y
Substitute 3^(x² + 1/x) for y:
dy/dx = (2x - 1/x²)ln(3)3^(x² + 1/x)
Add the second term:
dy/dx = (2x - 1/x²)ln(3)3^(x² + 1/x) + 3x²
——————————————————————————————————————
Note
d aáµ
—— = aáµÂ·ln(a)·u'
dx
————————————————
3^(x² + ¹ₓ̸) â This is aáµ
So,
d[x³ + 3^(x² + ¹ₓ̸)]
———————– = 3x² + 3^(x² + ¹ₓ̸)•ln(3)•(2x - ¹ₓ̸²) â ANSWER
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Verified answer
The derivative of the second term x³ is trivial:
d[x³]/dx = 3x²
One must use logarithmic differentiation on the first term:
let y = 3^(x² + 1/x) then ln(y) = (x² + 1/x)ln(3)
Differentiating both sides:
(1/y)dy/dx = (2x - 1/x²)ln(3)
Multiply both sides by y:
dy/dx = (2x - 1/x²)ln(3)y
Substitute 3^(x² + 1/x) for y:
dy/dx = (2x - 1/x²)ln(3)3^(x² + 1/x)
Add the second term:
dy/dx = (2x - 1/x²)ln(3)3^(x² + 1/x) + 3x²
——————————————————————————————————————
Note
d aáµ
—— = aáµÂ·ln(a)·u'
dx
————————————————
3^(x² + ¹ₓ̸) â This is aáµ
So,
d[x³ + 3^(x² + ¹ₓ̸)]
———————– = 3x² + 3^(x² + ¹ₓ̸)•ln(3)•(2x - ¹ₓ̸²) â ANSWER
dx
——————————————————————————————————————