如题所述
第1个回答 2019-03-21
38*19
=38*20-38
=760-38
=722
=38*20-38
=760-38
=722
第2个回答 2023-03-05
38×19
=38×(20-1)
=38×20-38×1
=760-38
=722本回答被网友采纳
=38×(20-1)
=38×20-38×1
=760-38
=722本回答被网友采纳
第3个回答 2019-03-21
38x19
=2x19x19
=2x(20-1)x(20-1)
=2x [ 20x20-2x20 +1 ]
=2x[ 400 -40 +1 ]
=800-80+2
=722本回答被网友采纳
=2x19x19
=2x(20-1)x(20-1)
=2x [ 20x20-2x20 +1 ]
=2x[ 400 -40 +1 ]
=800-80+2
=722本回答被网友采纳
第4个回答 2019-03-21
38X19
=38X20-38X1
=760-38
=722
=38X20-38X1
=760-38
=722