Helllp dau coroana urgent!!!!!

=155^3-154×155^2-154 (155+1)
=155^3-155^2×154-154×156
154×156=155^2 - 1 formula a × (a+2)=(a+1)^2 - 1
=155^3-155^2×154-155^2+1
=155^2 (155-154-1)+1
=155^2×0+1=0+1=1