Partial derivative with chain rule: check work

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SUMMARY

The discussion focuses on evaluating the function y = 10kl - √k - √l using the chain rule at t = 0, where k and l are defined as k = (t/5) + 5 and l = 5e^t/10. The correct application of the chain rule yields the expression ∂y/∂k * dk/dt + ∂y/∂l * dl/dt, with specific derivatives calculated for k and l. A transcription error was identified in the derivative of l, which should be -0.5l^(-0.5) instead of -0.5l^(-0.05). The final evaluation at t = 0 results in y(0) being approximately 51.

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Homework Statement



If possible, please check my work for any large errors.

y = 10kl - √k - √l
k = (t/5) + 5
l = 5e^t/10

Evaluate at t = 0 using chain rule.

Homework Equations



y = 10kl - √k - √l
k = (t/5) + 5
l = 5e^t/10

The Attempt at a Solution



= ∂y/∂k * dk/dt + ∂y/∂l * dl/dt
= (10l - 0.5K^-0.5)(1/5) + (10k - 0.5l^-.05)((e^(x/10))/2)

k(0) = 5
l(0) = 5
y(0) = ~9.95 + ~41.03 = ~51
 
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939 said:

Homework Statement



If possible, please check my work for any large errors.

y = 10kl - √k - √l
k = (t/5) + 5
l = 5e^t/10

Evaluate at t = 0 using chain rule.

Homework Equations



y = 10kl - √k - √l
k = (t/5) + 5
l = 5e^t/10

The Attempt at a Solution



= ∂y/∂k * dk/dt + ∂y/∂l * dl/dt
= (10l - 0.5K^-0.5)(1/5) + (10k - 0.5l^-.05)((e^(x/10))/2)
The above is close. The -0.5l^(-.05) term should be -0.5l^(-0.5). I don't know if that was a transcription error. Also, the exponential term would be clearer as (1/2)e(x/10).
939 said:
k(0) = 5
l(0) = 5
y(0) = ~9.95 + ~41.03 = ~51
k(0) and l(0) are fine, but I didn't check your other numbers.

One other thing. It's not good to start your first line with "=". For your problem, you should start with dy/dt = ...
 
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