Question

(-3-6-9-......-303) va rog sa mi se explice pas cu pas ca nu stiu :((( ​

Answer 1

 

$\displaystyle\bf\\Pasul~1:~~Dam~factor~comun~pe~(-3)\\\\Pasul~2:~~Folosim~formula~lui~Gauss\\\\Rezolvare:\\\\(-3-6-9-......-303)=\\\\=-3(1+2+3+...+101)=\\\\=-3\cdot\frac{101(101+1)}{2}=\\\\=-3\cdot\frac{101\cdot102}{2}=\\\\=-3\cdot101\cdot51=\\\\=-3\cdot5151=\boxed{\bf-15453}$