F.4 Maths

1/2x-1 +1/2x+1 =4/3
(2x+1)+(2x-1)/(2x-1)(2x+1)=4/3＜－－－通分母
4x/4x^2-1=4/3＜－－－－－(a+b)(a-b)=a^2-b^2
4x(3)=4(4x^2-1)<----交义相乘
16x^2-12x-4=0＜－－展開
4x^2-3x-1=0＜－－－約簡
(4x+1)(x-1)=0
x=-1/4 or 1

4x^4-17x^2+4=0
Let u be x^2 ,u^2=x^4
4u^2-17u+4=0
(4u-1)(u-4)=0
u=1/4 or 4
x^2=1/4 or4
x=1/2 ,-1/2 or 2 ,-2

1/(2x-1)+1/(2x+1)=4/3
2x+1+2x-1/(2x-1)(2x+1)=4/3(通分母)
4x/(4x^2-1)=4/3
12x=16x^2-4
16x^2-12x-4=0
4x^2-3x-1=0
(4x+1)(x-1)=0
4x+1=0 or x-1=0
x= -0.25 or 1

4x^4-17x^2+4=0
(4x^2-1)(x^2-4)=0
4x^2-1=0 or x^2-4=0
x^2=0.25 or x^2=4
x=+0.5 or -0.5 or +2 or -2

2007-03-03 23:00:10 補充：
做一元二次方要將所有野整埋一邊,另一邊係0 (ax^2 bx c=0)有得約就約..不過絕對唔可以約左有未知數o既項仲有如果有x二次方=正數x就會有正/負x因為負x o既平方都係正數..第二題去到四次方,不過唔洗驚,你當二次方x係y 四次方係y^2..咁就易睇好多