2X(X) +3X -4 =16

您好，我是 lop，高興能解答您的問題。

2X²+ 3X - 4 = 16
2X²+ 3X - 4 - 16 = 16 - 16
2X²+ 3X - 20 = 0
( 2X²+ 8X ) - ( 5X + 20 ) = 0
4X(X+4) - 5(X+4) = 0
(4X-5)(X+4) = 0
4X-5=0 or X+4=0
X = 5/4 or X = -4
X = -4 or 5/4

2011-09-20 17:54:45 補充：
抄錯了 sorry,

correction 001 :

2X²+ 3X - 4 = 16
2X²+ 3X - 4 - 16 = 16 - 16
2X²+ 3X - 20 = 0
( 2X²+ 8X ) - ( 5X + 20 ) = 0
2X(X+4) - 5(X+4) = 0
(2X-5)(X+4) = 0
2X-5=0 or X+4=0
X = 5/2 or X = -4
X = -4 or 5/2

2X(X) +3X -4 =16
2x^(2)+3x-4=16
2x^(2)+3x-20=0
(2x-5)(x+4)=0
2x-5=0 or x+4 =0
x=5/2 or x=-4

2x+3(-4)=16 2x-12=16 2x=28 X=14

2011-09-14 19:14:17 補充：
你個x吾是乘？。那2x^2+3x-4=16
2x^2+3x-20=0
(2x-5)(x+4)=0
X=5/2. X=-4

2011-09-14 19:21:25 補充：
lop....你把2X^2+8X 變4X(X+4)....

4X(X+4)=4X^2+8X

2X^2=/= (2X)^2 ....

2X(X)+3X-4=16
2X^2+3X-4=16
2X^2+3X-20=0
(2X-5)(X+4)=0
X=2.5 or X=-4