有幾題中2maths唔識...有冇高手幫手..20點.

1)x²-14x-72[里題可以嫁話要埋步驟thx~]
x²-14x-72
x²-18x + 4x -72
x(x - 18) + 4(x - 18)
(x – 18) (x +4)

2)x^(6)-1
[x^(3)]^2-1 = (x^3 + 1) (x^3 – 1)
= (x – 1) (x^2 +x + 1) (x +1)(x^2 –x + 1)

3)x^(4)+x²+1
Let y = x^2
y^2 +y + 1 cannot factorize ; please check!

4)開方108+開方12
108 = 3 x 16, 12 = 3 x 4
開方3 x開方16 +開方3 x開方4
開方3 x 4 +開方3 x 2
開方3 x (4 +2)
開方3 x 6 = 6 x 開方(3)

5)x(x+a)-10≡(x-b)(x+c),求a,b,c既可能值
x^2 +ax – 10 , x^2 + cx – bx –bc
x^2 +ax – 10 , x^2 + (c – b)x –bc

bc = -10, a = c – b
If c = 5, b = -2, a = 7
If c = 10, b = -1, a = 11

可能值:
c = +-10,+-1,+-5, +-2,
b = -+1,-+10,-+2,-+5
a = +-7, +-11

6)用兩個方法化簡x^(6)+y^(6)

x^(6)+y^(6) = (x^2)^3 + (y^2)^3
(x^2 + y^2) ((x^2)^2 – x^2y^2 + (y^2)^2)
(x^2 + y^2) ((x^4 – x^2y^2 + (y^4)

如果 x^(6) - y^(6) , 可用兩個方法化簡

2010-08-08 06:54:42 補充：
QUESTION (4) CORRECTION:
108 = 3 X 16 (錯)

108 = 3 x 36, 12 = 3 x 4
開方3 x開方36 +開方3 x開方4
開方3 x 6 +開方3 x 2
開方3 x (6 +2)
8 x 開方(3)

2010-08-08 07:05:28 補充：
(x^3 + 1) = (x +1) (x^2 - x + 1)
(x^3 – 1) = (x - 1) (x^2 +x + 1)

x^(6) - 1 = (x +1) (x^2 - x + 1)(x - 1) (x^2 +x + 1)

This is the same as (x – 1) (x^2 +x + 1) (x +1)(x^2 –x + 1)