已知A(x+1)+B(x-2)≡7x+13,其中A和B都是常數。求A和B的值。?
回答 (2)
2020-08-09 6:47 pm
A(x+1)+B(x-2)=7x+13
Ax+A+Bx-2B=7x+13
{A+B=7...(1)
{A-2B=13...(2)
(1)x4:4A+4B=28...(3)
(2)x2:2A-4B=26...(4)
(3)+(4)
(4A+4B)+(2A-4B)=28+26
6A=54
A=9
把A=9代入(4)
2(9)-4B=26
-4B=8
B=-2
所以A=9,B=-2
Ax+A+Bx-2B=7x+13
{A+B=7...(1)
{A-2B=13...(2)
(1)x4:4A+4B=28...(3)
(2)x2:2A-4B=26...(4)
(3)+(4)
(4A+4B)+(2A-4B)=28+26
6A=54
A=9
把A=9代入(4)
2(9)-4B=26
-4B=8
B=-2
所以A=9,B=-2
2020-08-12 6:28 pm
A(x+1)+B(x-2)
=Ax+A+Bx-2B
A+B=7
A-2B=13
A=9 B=-2
=Ax+A+Bx-2B
A+B=7
A-2B=13
A=9 B=-2
收錄日期: 2021-04-24 07:56:56
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https://hk.answers.yahoo.com/question/index?qid=20200809101902AACfqu2