Question

Tính :

\(A=3+6+9+...+99-2-5-8-...-98\)

giúp mk zới!

Answer 1

\(A=\left(3-2\right)+\left(6-5\right)+\left(9-8\right)+........+\left(99-98\right)\)

\(=1+1+1+.........+1\)( Có 33 số 1)

\(=1.33\)

\(=33\)

Answer 2

3+6+9+...+99=[(99-3):3+1](99+3)=33*102=3366

-2-5-8-...-98=-(2+5+8+...+98)=-{[(98-2):3+1](98+2)}=-33*100=-3300

A=3+6+9+...+99-2-5-...-98=3366-3300=66