Answer :

pids
[tex]df= \frac{df}{du} [/tex]Δx[tex]+ \frac{df}{dv} [/tex]Δv

I remember this formula. Differentiate your function with respect to u and v separately. 
Here you differentiate your function partially. 
 You may need Δu and Δv... 
Error %=[tex] \frac{df}{f}*100 [/tex]

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