For which of the following does f(r)−f(s)=f(r−s) for all values of r and s? Options:	A) f(a)=a^2	B) f(a)=a/2	C) f(a)=a+5	D) f(a)=2a−1	E) f(a)=|a|
To solve this easiest way is just put the value and see that if it equals or not.   with option 1. f(r) = r^2 and f(s) = s^2   so L.H.S = r^2 - s^2   and R.H.S = (r-s)^2 ==&gt; r^2 + s^2 -2rs.   so L.H.S not equal to R.H.S   with option 2. f(r) = r/2 and f(s) = s/2   L.H.S = r/2 - s/2 ==&gt; 1/2(r-s)   R.H.S = (r-s)/2   so L.H.S = R.H.S which is the correct answer.   f(a)=a/2
<result>B</result>
For which of the following does f(r)−f(s)=f(r−s) for all values of r and s?