1000.abc + abc = 1000.abc + 1.abc = abc( 1000 + 1 ) = abc.1001
\(1000\cdot abc+abc\)
\(=1000\cdot abc+1\cdot abc\)
\(=\left(1000+1\right)\cdot abc\)
\(=1001\cdot abc\)
1000 . abc + abc
= 1000 . abc - 1 . abc
= abc . ( 1000 + 1 )
= abc . 1001
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