99.9(8个9)*99.9(8个9)+199.9(8个9)
=99.9(8个9)*99.9(8个9)+2×99.9(8个9) +1
=【99.9(8个9)+1】的平方
=100……0(8个0)的平方
=100……0(16个0)
=10的16次方
末尾有16个0
99.9(8个9)*99.9(8个9)+199.9(8个9)
=99.9(8个9)*99.9(8个9)+2×99.9(8个9) +1
=【99.9(8个9)+1】的平方
=100……0(8个0)的平方
=100……0(16个0)
=10的16次方
末尾有16个0