a. First the fuzzy quantities x1*, x2*, y1*, and y2* have to be combined into a fuzzy vector with vector-characterizing function
Based on this fuzzy combined vector the estimatiors
are generalized to the fuzzy estimatiors 0* and 1* by applying the extension principle. For details compare the characterizing functions φj(·) in Remark 20.3 ad (d).
b. Here the fuzzy elements 0*, 1 *, and x* with corresponding membership functions have to be combined into a fuzzy 3-dimensional vector z*. Then the extension principle has to be applied to the function g(x) = θ0 + θ1 · x.