Question

tim X E N biet :

20\(⋮\)X va 25 \(⋮\)X

360\(⋮\)X ; 432\(⋮\)X va X lon nhat

Answer 1

Ta có :\(20⋮X\)    ;\(25⋮X\) \(\Leftrightarrow X\inƯC\left(20;25\right)\)

       \(20=2^2.5\) ; \(25=5^2\)

=> \(ƯC\left(20;25\right)=\left\{\pm1;\pm5\right\}\)

Mà : \(X\in N\Rightarrow x\in\left\{1;5\right\}\)

Answer 2

CMTT như trên => \(X\inƯCLN\left\{360;432\right\}\)

TA CÓ 

\(360=2^3.3^2.5\)                        ;\(432=2^4.3^3\)

\(\RightarrowƯCLN\left(360;432\right)=2^3.3^2=72\)

Vậy X = 72