👤

S=3/1x4+3/4x7+3/7x10+...+3/22x25

Răspuns :

3/1x4=1/1-1/4=
3/4x7=1/4-1/7
3/7x10=1/7-1/10
....
3/22x25=1/22-1/25
daca se aduna  ramane primul si ultimul termen

S=3/1x4+3/4x7+3/7x10+...+3/22x25= 1/1-1/25=(25-1)/25=24/25=0,96