a) 1+2+3+…+42=42⋅43:2=903.
1+3+5+…+59=1+2+3+…+60−(2+4+6+…+60)=30⋅61−2⋅15⋅31=900.
x=(3903+2⋅3900):29=
=3900(33+2):29, deci x=3900=(3300)3.
b) Folosim faptul că 81=62+52+42+22.
x=3900=(34)225=81⋅81224=
=(62+52+42+22)⋅3448=
=(6⋅3448)2+(5⋅3448)2+(4⋅3448)2+(2⋅3448)2.