Sum Rule
Key Questions
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The derivative for
y=f(x)-g(x)y=f(x)−g(x) works the same way as the derivative ofy=f(x)+g(x)y=f(x)+g(x) .y=f(x)-g(x) => dy/dx=f'(x)-g'(x) The quick proof is:
y=f(x)-g(x)=f(x)+(-1)g(x)
Using the sum rule and the constant rule:
dy/dx=f'(x)+(-1)g'(x)=f'(x)-g'(x) . -