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2014-09-21T21:50:46+03:00
A1=3*(2*0+1)
a2=3*(2*1+1)
a3=3*(2*2+1)
...................
an=3*[2(n-1)+1]
a) a100=3*(2*99+1)=3*199=597

b)3+3*(2*1+1)+3(2*2+1)+....+3(2*48+1)+3(2*49+1)=3*2(1+2+3+...+49)+3*50=
3*2*49*50/2+150=7350+150=7500