7+77+777+.....+ to n terms=7/81(10^n+1-9n-10)
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7+77+777+........+n
=7(1+11+111+......n)
=7/9(9+99+999+...n)
=7/9{(10-1)+(100-1)+(1000-1)+...+n}
=7/9{(10+100+1000+...n)-(1+1+1+...n)}
=7/9{10(10^n-1)/10-1 -n}
=7/9{10^n.10-10-9n/9}
=7/81[10^(n+1)-9n-10
LHS=RHS
Hence Proved.
Please ark it as a brainliest answer...
=7(1+11+111+......n)
=7/9(9+99+999+...n)
=7/9{(10-1)+(100-1)+(1000-1)+...+n}
=7/9{(10+100+1000+...n)-(1+1+1+...n)}
=7/9{10(10^n-1)/10-1 -n}
=7/9{10^n.10-10-9n/9}
=7/81[10^(n+1)-9n-10
LHS=RHS
Hence Proved.
Please ark it as a brainliest answer...
RivenDost:
Please also mark it a brainliest answer..
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