SOM x SOM (w8)

(a+b)(c+d) =
1. ac-ad+ac-bd
2. ac+ad-ac-bd
3. ac-ad . ac-bd
4. ab.cd
(c-5)(x+4) =
1. cx+4c-5x-20
2. cx-4c-5x+20
3. -20cx
4. cx-4c-5x-20
(x-4)(a-2) =
1. ax-2x-4a+8
2. ax-2x . 4a+8
3. -ax-2x-4a-8
4. 8ax
(2x+3y-7)(a-3) =
1. 2ax-6x+3ay-9y-7a+21
2. 2ax-6x-3ay-9y-7a-21
3. 2ax-6x+3ay . 9y-7a+21
4. 126axy
(x-1)(2a-5b+6)
1. 2ax-5bx+6x-2a+2b-6
2. 2ax+5bx-6x-2a-2b-6
3. 2ax-5bx+6x.2a+2b-6
4. 60abx