Verified answer

((a-2b)^2 - 4b^2)/a = (a^2 - 4ab + 4b^2 - 4b^2)/a = (a^2 - 4ab)/a = a - 4b

при а = 0.3 b = - 0.35

0.3 - (-0.35 x 4) = 0.3 - (-1.4) = 0.3 + 1.4 = 1.7