中二數學”衡等式”的問題....

講咁多做咩
直接做比你睇!

L.H.S. = Ax^2 - x - B
R.H.S. = (x+3)(x-C)
=x^2 + 3x - Cx - 3C

By comparing L.H.S. & R.H.S.,
Ax^2 = x^2 <= = = 通常見到有^2 .. 就姐係一樣架啦
A=1

-x = -x(C-3)
C-3=1
C=4 <= = = = R.H.S 果邊有x既話, 就抽佢出黎, 配合番LHS

-B = -3C
sub. C=4 into it.
-B=-12
B=12 <= = =搵完A,C之後, 就得番-B 同埋-3C , 所以sub 埋c落去就ko !

Ax^2-x-B=(x+3)(x-C)

RHS :
(x+3)(x-C)
=x^2 + (3-C)x -3C

By comparing the like terms
Ax^2=x^2
A=1

-x=(3-C)x
-1-3=-C
C=4

-B=-3C
-B=-3*4
B=12