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tamtam402
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Homework Statement
I'm trying to prove f(r) = A [itex]\bullet[/itex] (r - kz) is a linear operator, but I don't understand why it is linear.
Homework Equations
A function of a vector is called linear if:
f(r1+r2) = f(r1) + f(r2) and f(ar) = af(r)
The Attempt at a Solution
f(r1+r2) = A [itex]\bullet[/itex] (r1+r2 - kz) = A[itex]\bullet[/itex]r1 + A[itex]\bullet[/itex]r2 - A[itex]\bullet[/itex]kz
However, f(r1) + f(r2) = A[itex]\bullet[/itex]r1 - A[itex]\bullet[/itex]kz
+ A[itex]\bullet[/itex]r2 - A[itex]\bullet[/itex]kz
So, I just proved that the function is NOT a linear function, how great... :(
By the way, r = (x,y,z) in this book, if that changes anything.