Finding out values of unknowns in identities

Ax – 3 = Bx – A

By comparing the constants,
– 3 = – A
A = 3

By comparing the coefficients of x,
A = B
B = 3

∴ A = B = 3



希望幫到您！

I think 意見者：廢話 (001) has spoken with misconceptions towards IDENTITY.

　Identity, by definition, is a relation of equality which is always true (for all real values of x).

2008-11-15 01:54:23 補充：
(con't)
Therefore, by justifying only ONE case where x=0, the definition of "identity" still cannot be satisfied. It is not considered as a proof that "B can be all real numbers" or "回答者：sophialaisy 's answer is wrong".

回答者： sophialaisy
你的答案有問題：

Put x = 0, A = 3

Ax-3 = Bx-A
3(0)-3 = B(0)-3
-3 = -3

So, B can be all real number.

Ax-3 = Bx-A

A=B (1)
A=3 (2)
Sub (2) into (1),
A=B
3=B

A=3 and B=3