99.9 (2000个9) *99.9 (2000个9)+199.9 (2000个9)要用简便方法,

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99.9 (2000个9) *99.9 (2000个9)+199.9 (2000个9)要用简便方法,
99.9 (2000个9) *99.9 (2000个9)+199.9 (2000个9)
要用简便方法,

99.9 (2000个9) *99.9 (2000个9)+199.9 (2000个9)要用简便方法,
99.9 (2000个9) *99.9 (2000个9)+199.9 (2000个9)
=99.9 (2000个9) *99.9 (2000个9)+2×99.9 (2000个9)+1
=〔99.9 (2000个9)+1〕^2
=100……0(2000个0)^2
=10^4000
即10的4000次方

9999...999*9999.999+1000.00+9999.999=9999...999(1+9999.999)+1000.000=9999...99900000000(2000个0)+100000.000(2000个0)=1000000..0000(4000个0)

99.....9 (2000个9) *99....9 (2000个9)+199....9 (2000个9)
=(1000(2001个0)-1)^2+199....9 (2000个9)
=10^2002-2000(2000个0)+199....9 (2000个9)+1
=10^2002
是10的4004次方