identify the functions that exhibit a removable discontinuity.f(x) = x2+4x-21/x2-13x+42 g(x) = 2x2-5x+12/2x+3 h(x) = x-3/x2-9i(x) - x-8x+15/x-5j(x) = x+4/-2x+8 k(x) = 2x2+x-15/2x-5