Question

Calculati:


a) a=46+52+58+....+1006
b b+72+86+95+....+950

Answer 1

a) a=46+52+58+....+1006

progresie aritmetica cu an=1006, a1=46 si ratia r=6 (cresc din 6 in 6)

an=a1+(n-1)×r

1006=46+(n-1)×6

1006=46+6n-6⇒966=6n

n=161

S=[(an+a1)×n]:2=(46+1006)×161]:2=(1052×161):2=84686

S=84686