Question

Calculați 3 plus 5 plus 7 plus puncte puncte plus 357​

Answer 1

3 + 5+...+357 =

=2+3+4+...+356+357-(2 +4 + ...+356)=

=357x 358/2 - 2( 1+2+...+178)=

=357x358/2-2 x (178x179)/2=

=357x 179 - 2 x 178 x 179=

=179 ( 357 - 356)=

=179 x 1=

=179