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s=8plus 13plus18plus23plus....plus138

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ALIANTA50
 ESTE O SUMA SPECIALA
S=8+13+18+23+      + 138
FOLOSESTI FORMULA LUI GAUS
PASUL 5


Renatemambouko
8+13+18+23+......138 =
8+18+28+38+48+....138+13+23+33+43+.....133=
8*14+10(1+2+3....13)+3*13+10(1+2+3...13) =
112+10[13(13+1):2]+39+10[13(13+1):2}=
112+10*13*7+39+10*13*7= 112+910+39+910=1971