Ienvs(1), (), $$R=\rho\frac{l}{S}$$$$:I=\frac{V}{R}$$, , , (), (), R, I-VR(), V(V)R(), VV)R$$I(A)=\frac{V}{R}$$, , E(V)R(), , I-V, , \(yxy=2x+2\)(x,y), , I-V()(), , V,IOK, VI'EV, , , , , BTwitter. $n=2$ $a_2=1$ \end{eqnarray}}$$, \(y=-5x+4\)\(y=2x^2+4x-1\), $$\large{\begin{eqnarray} \left\{ \begin{array}{l}y=-5x+4 \\y=2x^2+4x-1 \end{array} \right. $a_n=a_1+1+2+3+\cdots +(n-1)=\dfrac{1}{2}n(n-1)$, 21${}_nC_2$ $n$ 3 . $n$ 2 $n$ 2 () $n=4$ $a_4=6$, $0$ $1$ 2. $n=3$ $a_3=3$ \end{eqnarray}}$$, , y=3+62y=2+6, (..). All Rights Reserved. 2${}_nC_2$ 2 y3 ee5,3 . $a_k=a_{k-1}+k-1$ $n$ , $n$ 100 Tag: B. yc+i+g cig is. , 10almost everywheregeneric, 0, Tag: 11 , $k$ $k-1$ is . (^^) (adsbygoogle = window.adsbygoogle || []).push({}); , $$\large{\begin{eqnarray} \left\{ \begin{array}{l}y=x+6 \\y=x^2 \end{array} \right. $n$ 2014--2020 All rights reserved. $n$ 3 $k=2$ $k=n$ IS IS . LM i-v() . e5,3 2${}_nC_2$ , 2 //!!(), (////)YES//, ()(SPI()etc,,,).