Ответ: R1=50 Ом   α=0,004   t1=20    t2=-30   R2=?===R1=Ro*(1+α*t1)R2=Ro*(1+α*t2)Ro=R1/(1+α*t1)R2=R1*(1+α*t2)/(1+α*t1)=50*(1-0.004*30)/(1+0.004*20)=40.7 Ом========================