作业帮若P=a²+3ab+b²,Q=a²-3ab+b²,则代数式P-[Q-2P-（-P-Q）]=___.
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/05 04:34:07
![若P=a²+3ab+b²,Q=a²-3ab+b²,则代数式P-[Q-2P-（-P-Q）]=___.](/uploads/image/z/1104643-19-3.jpg?t=%E8%8B%A5P%3Da%26%23178%3B%2B3ab%2Bb%26%23178%3B%2CQ%3Da%26%23178%3B-3ab%2Bb%26%23178%3B%2C%E5%88%99%E4%BB%A3%E6%95%B0%E5%BC%8FP-%5BQ-2P-%EF%BC%88-P-Q%EF%BC%89%5D%3D___.)
若P=a²+3ab+b²,Q=a²-3ab+b²,则代数式P-[Q-2P-（-P-Q）]=___.
若P=a²+3ab+b²,Q=a²-3ab+b²,则代数式P-[Q-2P-（-P-Q）]=___.
若P=a²+3ab+b²,Q=a²-3ab+b²,则代数式P-[Q-2P-（-P-Q）]=___.
P-[Q-2P-（-P-Q）]=P-[Q-2P+P+Q]=P-(2Q-P)=P-2Q+P=2P-2Q=2*(P-Q)=2[(a^2+3ab+b^2)-(a^2-3ab+b^2)]=2[a^2+3ab+b^2-a^2+3ab-b^2]=12ab
P-[Q-2P-（-P-Q）]=2(P-Q)=12ab
P=a²+3ab+b²=（a+b）^2+ab Q=a²-3ab+b²=（a+b）^2-5ab，P-Q=（a+b）^2+ab -{（a+b）^2-5ab}=6ab
P-[Q-2P-（-P-Q）]=P-(Q-2P+P+Q)=P-Q+2P-P-Q=2P-2Q=2(P-Q)=2X6ab=12ab