A) (7 - 3V3) / 33 = (7 - 3V3) * (7 + 3V3) / (33 * (7 + 3V3) = (7^2 - (3V3)^2) /
/ (33 * (7 + 3V3)) = (49 - 27) / (33*(7 + 3V3) = 22 / (33(7 + 3V3)) =
= 2 / (21 + 9V3)
б) (Va + Vb) / a = (Va + Vb) * (Va - Vb) /(a(Va - Vb)) = ( (Va)^2 - (Vb)^2 ) /
/(a(Va - Vb)) = (a - b) / (a(Va - Vb))