Question

Tính tổng sau:

1.3+2.4+3.5+4.6+.....+97.99+98.100

Answer 1

Cái này nữa, chữ hơi xấu, thông cảm nha.

Answer 2

1.3+2.4+3.5+4.6+.....+97.99+98.100 

\(=2^2-1+3^2-1+....+99^2-1\)

\(=1^2+2^2+3^2+....+99^2-99\)

\(=\frac{99.100.196}{6}-99\)

\(=328251\)

Answer 3

1.3+2.4+3.5+4.6+.....+97.99+98.100

= 2² - 1 + 3²+...+99² - 1
= 1² + 2² + 3² + 99² - 99
=\(\frac{99.100.199}{6}\) - 99
= 328251

Answer 4

1.3+2.4+3.5+4.6+...+97.99+98.100

=2^2-1+3^2-1+4^2-1+.....+99^2-1

=1^2+2^2+3^2+.....+99^2-99

=99.100.199/6-99

=328521