Bài 3: Rtđ= R1+R2+R3+...+Rn=1+2+3+...+2015
Tổng trên có: (2015-1):1+1=2015(số hạng)
=> Rtđ=(2015+1).2015:2=2031120 ([tex]\Omega[/tex]
Bài 4: [tex]\frac{1}{Rtm}=\frac{1}{R1}+\frac{1}{R2}+\frac{1}{R3}+...+\frac{1}{Rn}[/tex]
[tex]<=> \frac{1}{Rtm}=\frac{1}{1}+\frac{1}{\frac{1}{2}}+\frac{1}{\frac{1}{3}}+...+\frac{1}{\frac{1}{2015}}[/tex]
[tex]<=> \frac{1}{Rtm}=1+2+3+...+2015[/tex]
[tex]<=> \frac{1}{Rtm}=2031120[/tex]
[tex]=> Rtm=\frac{1}{2031120}(\Omega )[/tex]