Разложи на множители (u+20v)^2−(20u+v)^2

(u+20v)^2−(20u+v)^2=(u+20v-20u-v)(u+20v+20u+v)=(19v-19u)(21u+21v)=19*21(v-u)(u+v)

(u+20v -(20u+v))(u+20v+ 20u+v)= (u+20v-20u-v)(21u +21v)=(19v-19u)(21u+21v)= 19*21(v-u)(v+u)==399(v-u)(v+u)