123²-122×124
=123²-(123-1)(123+1)
=123²-(123²-1)
=123²-123²+1
=1
﹙2a－1﹚²－4﹙a－1﹚﹙a＋1﹚
=（4a²-4a+1）-4（a²-1）
=4a²-4a+1-4a²+4
=-4a+5﹙2/3ab²﹚×﹙-2a﹚³1+﹙-½﹚负二的平方－﹙3.14－π)﹙2/3ab²﹚×﹙-2a﹚³ =2/3ab²×(-8a³ )=-16a²/3b²1+﹙-½﹚负二的平方－﹙3.14－π)=1+﹙-½﹚×4-3.14+π=1-2-3.14+π=π-4.14（2a-b)²+(a+1-b)(a+1+b)-(a+1)²(2a-b)²+(a+1-b)(a+1+b)-(a+1)²=(2a-b)²+[(a+1)²-b²]-(a+1)²=(2a-b)²-b²=(2a-b+b)(2a-b-b)=2a(2a-2b)=4a²-4ab