Question

Arătați că numărul a= 17 + 17 * 2+17* 3 +....... +17* 17 este pătrat perfect

dau 160 de puncte​

Answer 1

 

$\displaystyle\bf\\17+17\times2+17\times3+...+17\times17=\\\\=17(1+2+3+...+17)\\\\=17\times\frac{17\((17+1)}{2}=\\\\=17\times\frac{17\times18}{2}=\\\\=17\times17\times9=17^2\times3^2=(17\times3)^2=51^2=pp$