Question

1+3+...+41 ajutati.ma plisss
7

Answer 1

1+3+5+7+9+11+13+15+17+19+21+23+25+27+29+31+33+35+37+39+41

Answer 2

( 1+2+3+4+...+41) - ( 2+4+6+..+40)=
= $\frac{41 ori 42}{2}$ - 2· ( 1+2+3+...+20)=
 =$\frac{41 ori 42}{2}$ - 2· $\frac{20 ori 21}{2}$ 

de aici cred ca te descurci :)