In the figure, diodes 1 and 2 both are in reverse bias and in reverse bias, diode does not conduct, so we may replace diodes 1 and 2 as open circuit (OC)
Here, resistors of resistances 8Omega,2Omega and 6Omega are in series. So, equivalent resistance between points A and B RAB=8+2+6 RAB=16Ω