(1)+(1+1)+(1+1+1)+•••+(1+1+1+•••n-1 times)=•••••••••
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Answer:
n[n-1]/2
Step-by-step explanation:
1+[1+1]+[1+1+1]+...........................[1+1+1+.....n-1]=1+2+3+4+5+6+7+8+9+10+11+.........+n-1
=n[n-1]/2
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