Sagot :
pour la 1ére
1+2 = 4-1
= 3= 3 donc vrai
la 2ème
1+2+4 = 8-1
7 = 7 donc vrai
la 3ème
1+2+4+8 = 16-1
15 = 15 donc vrai
2^(0)+2^(1)=2^(2)-1
2^(0)+2^(1) = 1 + 2 = 3
2^(2)-1 = 4 -1 = 3
Donc 2^(0)+2^(1)=2^(2)-1
2^(0)+2^(1)+2^(2)=2^(3)-1
2^(0)+2^(1)+2^(2) = 3 +4 = 7
2^(3)-1 = 8 -1 = 7
Donc 2^(0)+2^(1)+2^(2)=2^(3)-1
2^(0)+2^(1)+2^(2)+2^(3)=2^(4)-1
2^(0)+2^(1)+2^(2)+2^(3) = 7 + 8 = 15
2^(4)-1 = 16 -1 = 15
Donc 2^(0)+2^(1)+2^(2)+2^(3)=2^(4)-1