Hello. I am studying for my exam and just came across a problem that states I must take a partial derivative of a utility function. I am kind of confused since it's been a while since I've done this. The answer in the book appears to be missing a decimal point. But I also need a refresher on partial derivatives it seems . Please note that w1 and w2 are just terms.

The utility function is and we must figure out it's derivative as in

i got dw2/dw1 =

from here i am unsure as to why this is equal to

any help is appreciated

thank you

chris