Question

Tính:

A =1^2+2^2+3^2+...+97^2+98^2

B =1.99+2.98+3.97+...+98.2+99.1

Answer 1

1230 nha

Answer 2

 

B =1.99+2.98+3.97+...+98.2+99.1

Answer 3

=1.99+2.(99-1)+3.(99-2)+...+98.(99-97)+99(99-98)

=99.(1+2+3+4+...+98+99)-(2+2.3+3.4+...+97.98+98.99)

=99.(1+99).99/2-98.99.100/3

=99.50.99-98.33.100

=490050-323400

=166650

Answer 4

=1.99+2.(99-1)+3.(99-2)+...+98.(99-97)+99(99-98)

=99.(1+2+3+4+...+98+99)-(2+2.3+3.4+...+97.98+98.99)

=99.(1+99).99/2-98.99.100/3

=99.50.99-98.33.100

=490050-323400

=166650