Given that \(\sum_{r=1}^{k}(7+5r)=1190\) ,(i) Show that \((5k+119)(k-20)=0.\)(ii) Hence find the v - চর্চা

Given that \(\sum_{r=1}^{k}(7+5r)=1190\) ,(i) Show that \((5k+119)(k-20)=0.\)(ii) Hence find the v - চর্চা