Ioana364218ask
a fost răspuns

l
S=178+1 2 3 ... 902
S=1+2+3...432
S=160+ lout 1097 ...+507
S=52+53+59+...+ 2011
S: 2+3+4+...+308
S: 8+4+5+...176

Răspuns :

Asuasiask

Explicație pas cu pas:

S=n(n+1):2

S=1+2+3+...432

S=432(432+1):2

S=432x433:2

S=93528

S=52+53+54+...+2011

n=(2011-52):1+1

n=1959+1

n=1960

S=1960(2011+25):2

S=1960*2036:2

S=1960*1018

S=2+3+4+...+308

n=(308-2):1+1

n=306+1

b=307

S=307(308+2):2

S=307*310:2

S=307*155

S=47585