[tex]1) \ a_{1}=5\\\\a_{7} =41\\\\a_{7}=a_{1}+6d \\\\6d=a_{7} -a_{1} =41-5=36\\\\d=6\\\\Otvet:\boxed{d=6}[/tex]
[tex]2) \ BO=8 \ cm\\\\BC=22 \ cm\\\\BD=12 \ cm\\\\DC=?[/tex]
Если DO - биссектриса , то :
[tex]\dfrac{DC}{BD}=\dfrac{CO}{BO} \\\\BC=22 \ \ \Rightarrow \ CO=BC-BO=22-8=14cm\\\\DC=\dfrac{BD\cdot CO}{BO} =\dfrac{12\cdot 14}{8}=\boxed{21 \ cm}[/tex]
