D = x/x-4 and x 2} X-4x-5 The domain of R(x) = x2+2x-8 is the set of all real numbers, except those values of .x that make x2 + 2x - 8 equal to 0. These values are determined by solving x2 + 2x - 80. x2 + 2x - 80 (x+4)(x - 2) = 0 0 or -4 or x 2​