Question

两道数学题!!! 过程 求助!!!!!!!!!!!!!

1.(a+b-c)(-a+b+c)=【b+( )】【b-( )】填空
2.已知1/a-1/b=4,则a-2ab-b/2a-2b+7ab=_______ 填空

Answer 1

1.(a+b-c)(-a+b+c)=[b+(a-c)][b-(a-c)]
2.1/a-1/b=4
b-a=4ab
a-2ab-b/2a-2b+7ab
=(a-b)-2ab/2(a-b)+7ab
=-6ab/-8ab
=3/4

Answer 2

1.(a+b-c)(-a+b+c)=【b+(a-c)】【b-(a-c)】

Answer 3

1/a-1/b=4
b-a=4ab
a-2ab/(2a-2b)+7ab
=(a-b)-2ab/2(a-b)+7ab
=-6ab/-8ab
=3/4

Answer 4

【b+(a-c)】【b-(a-c)】
3/4