Oblicz sume S20 ciagu arytmetycznego 3,8,13,18 rozwiaz rownanie 4×+7 ---------- =×+3 ×+1

[latex]a_{1}=3\ a_{2}=8\ r=a_{2}-a_{1}=8-3=5\ \ S_{20}=frac{2a_{1}+19r}{2}cdot 20=frac{6+95}{2}cdot 20 = 101cdot 10=1010[/latex] [latex]frac{4x+7}{x+1}=x+3\ 4x+7=(x+3)(x+1)\ 4x+7=x^2+4x+3\ x^2-4=0\ (x+2)(x-2)=0\ x+2=0 vee x-2=0\ x=-2 vee x=2\ xin{-2,2}[/latex]