Răspuns :
3+6+9+12+...+429=
=3×(1+2+3+4+...+143)=
=3×(144×143:2)=
=3×(72×143)=
=3×10296=
=30888
=3×(1+2+3+4+...+143)=
=3×(144×143:2)=
=3×(72×143)=
=3×10296=
=30888
3+6+9+12+....+429=
=3(1+2+3+4+...+143)
=3( 144*143 :2)
=3*10296
=30888
=3(1+2+3+4+...+143)
=3( 144*143 :2)
=3*10296
=30888