T1=2pi√(l1 / g); T2=2pi√(l2 / g);выражаем длину через период:l1=(g*T1^2)/(4*pi^2). l2=(g*T2^2)/(4*pi^2). l2-21=0.1 м; (g*T2^2)/(4*pi^2)-(g*T1^2)/(4*pi^2)=0.1 тк Т2=Т1+0.1 то (g*(T1+0.1)^2)/(4*pi^2)-(g*T1^2)/(4*pi^2)=0.1=>g((T1+0.1)^2-T1^2)=0.4pi^2 =>0.1g(2T+0.1)=0.4pi^2=>2T+0.1=(0.4pi^2)/0.1g=>T=((0.4pi^2)/0.1g-0.1)/2 T=1.92 c