F.2 Maths

5a)　(x+y)(x-y) <-----用公式 (a+b)(a-b)=a square + b square
= x square + y square
square = 2次方

b) (2x+5)(2x-5) <------ 用同一公式
= (2x) all square + 5 square
= 4x square + 25 <------- 4 已經2次方左 ,而x就未square ,所以個2次方只係x 所擁有

6a) (-x-y)(-x+y) <------ 用同一公式
= (-x) square + y square <------唔好比條數嚇倒 ,睇真d ,只係個x前面多左個負數 ,其實都係用同一條公式

b) (2-3x)(2+3x) <------ 用同一公式
= 2 square + (3x) all square
= 4+ 9x square <------- 9 已經2次方左 ,而x就未square ,所以個2次方只係x 所擁有

7a) (x+y)^2
= 2x+ 2y

b) (x-y)^2
= 2x-2y

8a) (5x+ 6y)^2
= 10x+12y

b) (3x-7y)^2
= 6x-14y

p.s.7同8題只係將*2 "成"入( )內的每一個數值就得 ,小心"符號"(正負數)喔!!

2007-10-14 15:02:43 補充：
sorry 7 同 8題計錯左 should　be:7a) (x+y)^2 = x square +2xy + y squareb) (x-y)^2 = x square -2xy + y square我之前看錯了"^"的意思 ,以為是"x"號~

2007-10-14 15:03:02 補充：
8a) (5x+ 6y)^2 = 25 x square + 2(5x)(6y) + 36 y square= 25 x square + 150xy + 36 y sqaure b) (3x-7y)^2 = 9 x square - 2(3x)(7y) + 49 y square = 9 x square - 42xy + 49 y square

2007-10-14 15:09:37 補充：
7a 同 8a 用左公式 (a+b) all squre = a square + 2ab +b square7b 同 8b 用左公式 (a-b) all squre = a square - 2ab +b square8a 同ｂ要注意的是：如8a的尾２的25 x square + 2(5x)(6y) + 36 y square ,25同36 已經2次方左 ,而x就未square ,所以個2次方只係x同y 所擁有

5.a) (x+y)(x-y)
=x^2-y^2

b)(2x+5)(2x-5)
=4x^2-25

6.a)(-x-y)(-x+y)
=x^2-y^2

b)(2-3x)(2+3x)
=4-9x^2

7.a)(x+y)^2
=x^2+2xy+y2

b)(x-y)^2
=x^2-2xy+y^2

8.a)(5x+ 6y)^2
=(5x)^2+2(5x)(6y)+(6y)^2
=25x^2+60xy+36y^2

b)(3x-7y)^2
=(3x)^2-2(3x)(7y)+(7y)^2
=9x^2-42xy+49y^2

5a. (x+y)(x-y)
=x^2+xy-xy-y^2
=x^2-y^2

5b. (2x+5)(2x-5)
=4x^2+10x-10x-25
=4x^2-25

6a. (-x-y)(-x+y)
=x^2+xy-xy-y^2
=x^2-y^2

6b. (2-3x)(2+3x)
=4-6x+6x-9^2
=4-9^2

7a. (x+y)^2
=(x+y)(x+y)
=x^2+xy+xy+y^2
=x^2+2xy+y^2

7b. (x-y)^2
=(x-y)(x-y)
=x^2-xy-xy+y^2
=x^2-2xy+y^2

8a.)(5x+ 6y)^2
=(5x+6y)(5x+6y)
=25x^2+30xy+30xy+36y^2
=25x^2+60xy+36y^2

8b.)(3x-7y)^2
=(3x-7y)(3x-7y)
= 9x^2-21xy-21xy+49y^2
=9x^2-42xy+49y^2

5 a) x^2 - y^2
5 b) 4x^2 - 25

6 a) x^2 - y^2
6 b) 4 - 9x^2

7 a) x^2 + 2xy + y^2
7 b) x^2 -2xy + y^2

8 a) 25x^2 +60xy + 36y^2
8 b) 9x^2 -42xy + 49y^2

５ａ)(x ^ 2) - (y ^ 2) b) 4(x ^ 2) - 25
6a)(x ^ 2) - (y ^ 2) b) 4 - 9(x ^ 2)
7a) (x ^ 2) + 2xy + (y ^ 2) b) (x ^ 2) - 2xy + (y ^ 2)
8a)25(x ^ 2) + 30xy + 36(y ^ 2) b) 9(x ^ 2) - 21xy + 49(y ^ 2)