數學功課#1(中二生入來,很易)(急!)

3a) -4a+2b
4a) 10-9x
8) bx-4by-6bx-by
10) 6by-5b-2by+b

2.-2x+6y
14.30(a的2次)-36a25a-30
25. 18(a的2次)+2ax+9ax+(x的2次)

最基本就係搵個Same variable,先作出加減
Ⅰ:化簡下列各多項式.
3.(a)
-4a+3b-b <---照減
=-4a+2b

4.(a)
2x2-4x-5x+3x2
=4-9x+6
=9x+6+4
=9x+10

8.(b)
(x-4y)-(6x-y) <---拆括號,(x-4y)係正數,照寫就ok,-(6x-y)係負數,要顛倒咁拆
=x-4x-6x+y
=-6x-4x+x+y
=-9x+y

10.(b)
(6y-5)-(2y+1)
=6y-5-2y-1
=6y-2y-5-1
=4y-6

Ⅰ:用展開法求下列各多項式的積.
First,睇下example,應該就易明d
Ex:有個袋入面,有1個apple同1個orange,即a+b,而我又有2袋,so條式係2(a+b),如果我拎晒d apple同d orange出黎,我就有2個apple and 2個orange,即2a+2b
2.
-2(x-3y)
=(-2)(x)+(-2)(-3y)
=-2x+6y <---我通常都會一跳就跳到呢個步驟

14.
(6a+5)(5a-6)
=(6a)(5a-6)+(5)(5a-6)
=30a^2-36a+25a-30
=30a^2-11a-30

25.
(2a+x)(9a+x)
=(2a)(9a+x)+(x)(9a+x)
=18a^2+2ax+9ax+x^2
=18a^2+11ax+x^2

Hope I can help you.

3.(a) -4a+3b-b
=-4a+2b

4.(a) 2x2-4x-5x+3x2
=4-9x+6
=10+9x

8.(b) (x-4y)-(6x-y)
=x-4y-6x+y
=-5y-3y

10.(b) (6y-5)-(2y+1)
=6y-5-2y-1
=4y-6

2. -2(x-3y)
=-2x+6y

14. (6a+5)(5a-6)
=6a(5a-6)+5(5a-6)
=30a^2-36a+25a-30
=30a^2-11a-30

25. (2a+x)(9a+x)
=2a(9a+x)+x(9a+x)
=18a^2+2ax+9ax+x^2
=18a^2+11ax+x^2

3a) -4a+3b-b
= -4a+2b
=2b-4a

4a) 2x2-4x-5x+3x2
= 4-9x+6
= 10-9x

8b) (x-4y)-(6x-y)
= x-4y-6x+y
= -5x-3y

10b) (6y-5)-(2y+1)
= 6y-5-2y-1
= 4y-6


2) -2(x-3y)
= -2x+5y
= 5y-2x

14) (6a+5)(5a+6)
= 30a^2(2次方)+36a+25a+30
= 30a^2(2次方)+61a+30

25) (2a+x)(9a+x)
= 18a^2(2次方)+2ax+9ax+x^2(2次方)
= 18a^2(2次方)+11ax+x^2(2次方)