Question

Calculati 2+5+8+.......+44

Answer 1

2+5+8+.......+44 - progresie aritmetica
an=a1+(n-1)×r
an=44, a1=2  si r(ratia-pasul)=3
44=2+(n-1)×3⇒44=2+3n-3⇒45=3n⇒n=15
n=15
S=[(a1+an)×n]:2=[(2+44)×15]:2=345

2+5+8+.......+44 =345

Answer 2

S=2+5+8+............+44
S=44+41+38+............+2
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2S=46+46+46+....................+46
2,2+3X1,2+3X2,...............,2+3X(46:2)=23
2S=46X24
2S=1104
S=1104:2
S=552