BCNN(105;140)=420

BCNN(105;140)=420

TK

B(8) ={0; 8; 16; 24; 32; 40; 48...}

B(12) = {0; 12; 24; 36; 48;...}

BC(8; 12) = {0; 24; 48; ...}

Do \(1\le a;b;c\le6\Rightarrow\left\{{}\begin{matrix}\left(a-1\right)\left(b-1\right)\left(c-1\right)\ge0\\\left(6-a\right)\left(6-b\right)\left(6-c\right)\ge0\end{matrix}\right.\)

\(\Rightarrow\left(a-1\right)\left(b-1\right)\left(c-1\right)+\left(6-a\right)\left(6-b\right)\left(6-c\right)\ge0\)

\(\Leftrightarrow5\left(ab+bc+ca\right)-35\left(a+b+c\right)+215\ge0\)

\(\Leftrightarrow5\left(ab+bc+ca\right)-205\ge0\)

\(\Rightarrow ab+bc+ca\ge41\)

\(P_{min}=41\) khi \(\left(a;b;c\right)=\left(1;5;6\right)\) và các hoán vị

12=2².3;30=2.3.5=> UCLN(a,b)=6=>UC(a,b)=U(6)={1;2;3;6}

    BCLN(a,b)=2².3.5=60=>BC(a,b)=B(60)={0;60;120;180;...}

ƯC(12,30) = {1;2;3;6}

BC(12,30) = {60;120;180;...}

ƯC(12,30):(1;2;3;6)

BC(12;30):(60;120;180)