For ten points, identify this property held by a function like f(x)=3x.
The expected value of a random variable has this property, but its variance does not. This property is held by a homothecy centered at the origin. A func- tion satisfying Cauchy's functional equation has this property if it is continuous at at least one point, if it is bounded on any interval, or if it is monotone on any interval. Functions must be   additive and homogenous of degree 1 to satisfy this property. This property is held by di erentiation and integration with a  xed starting point. This property fails to be held by polynomials whose degree exceeds 1. For ten points, identify this property held by a function like f(x)=3x.
The expected value of a random variable has this property, but its variance does not.
linearity [accept word forms]