Question

Tìm STN a thỏa mãn 100<a<500 . Và a chia hết cho 24 a:80

Answer 1

\(a⋮24\) hay  \(BC\left(24\right)=a\)

\(BC\left(24\right)=\left\{\pm24;\pm48;\pm72;\pm96;\pm120;\pm144;\pm168;...;\pm480\right\}\)

\(a⋮80\) hay \(BC\left(80\right)=a\)

\(BC\left(80\right)=\left\{\pm80;\pm160;\pm240;...;\pm480\right\}\)

mà a thỏa mãn \(100< a< 500\)

nên \(a\in\left\{\pm240;\pm480\right\}\)

vậy \(a\in\left\{\pm240;\pm480\right\}\)

Answer 2

a chia hết cho 24, a chia hết cho 80 => a thuộc BC(24,80)

Ta có : 24 = 2³.3

            80 = 2⁴.5

=> BCNN(24,80) = 2⁴.3.5 = 240

=> BC(24,80) = B(240) = {0 ; 240 ; 480 ; 720 ; ....}

Vì 100< a<500 => a = { 240 ; 480 }

Answer 3

Ta có:

\(\orbr{\begin{cases}a⋮24\\a⋮80\end{cases}\Rightarrow a\in BC\left(24;80\right)}\)

\(BCNN\left(24;80\right)=\)

\(24=2^3.3\)

\(80=2^4.5\)

\(BCNN\left(24;80\right)=2^4.3.5=240\)

\(BC\left(24;80\right)=\left(0;240;480;720;..\right)\)

Vì \(100< a< 500\Rightarrow a=\left\{240;480\right\}\)