若ab=6,a-b=5,则a^2b-ab^2=30,a^2b+ab^2=?

来源:学生作业帮助网 编辑:六六作业网 时间:2024/11/24 14:29:33
若ab=6,a-b=5,则a^2b-ab^2=30,a^2b+ab^2=?若ab=6,a-b=5,则a^2b-ab^2=30,a^2b+ab^2=?若ab=6,a-b=5,则a^2b-ab^2=30,

若ab=6,a-b=5,则a^2b-ab^2=30,a^2b+ab^2=?
若ab=6,a-b=5,则a^2b-ab^2=30,a^2b+ab^2=?

若ab=6,a-b=5,则a^2b-ab^2=30,a^2b+ab^2=?
a^2b-ab^2
=ab(a-b)
=6*5
=30
a-b=5
(a-b)^2=25 a^2+b^2-2ab=25 a^2+b^2=25+2ab=25+2*6=37
(a+b)^2=a^2+b^2+2ab=37+2*6=49
a+b=7或-7
a^2b+ab^2
=ab(a+b)=6*(±7)
=±42

方法一 直接求出a,b
ab=6,a-b=5联立求解,a=-1,b=-6或者a=6,b=1
代入a^2b+ab^2=42或者-42
方法二
(a-b)^2=a^2-2ab+b^2=5^2=25
a^2+b^2=25+2ab=25+2*6=37
(a+b)^2=a^2+2ab+b^2=37+2*6=49
a+b=7或者-7
a^2b+ab^2=ab(a+b)=42或者-42