How do you differentiate #f(x)=x+x-2x# using the sum rule?

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Answer 1 · 2015-12-19T16:11:26

According to the sum rule,

#f'(x)=d/dx[x]+d/dx[x]-d/dx[2x]#

#d/dx[x]=1#

#d/dx[2x]=2#

Thus,

#f'(x)=1+1-2=color(red)(0#

This should be fairly obvious because #f(x)# can be simplified from the beginning to find that #f(x)=0#, so #f'(x)=0# as well.