有數學唔識做？？

1.(a+2b)+(a-3b-c)
=a+a+2b-3b-c
=(1+1)a+(2-3)b-c
=2a-b-c


2.(3x+y)-(2x-2y-3z)
=3x+y-2x+2y+3z
=(3-2)x+(1+2)y+3z
=x+3y+3z

3.(6p+4q)-(5q-4r)
=6p+4q-5q+4r
=6p+(4-5)q+4r
=6p-q+4r

4.(5x+7y)-(8x-6y-3z)
=5x+7y-8x+6y+3z
=(5-8)x+(7+6)y+3z
=-3x+13y+3z

1.(a+2b)+(a-3b-c)
=a+a+2b-3b-c
=(a+a)+(2-3)b-c
=2a-b-c

2.(3x+y)-(2x-2y-3z)
=3x-2x+y-2y-3z
=(3-2)x+(1-2)y-3z
=x-y-3z

3.(6p+4q)_(5q-4r)
=6p+4q-5q+4r
=6b+(4-5)q+4r
=6b-q+4r

4.(5x+7y-(8x-6y-3z)
=5x-8x+7y+6y+3z
=(5-8)x+(7+6)y+3z
=-3x+13y+3z

2007-05-29 00:04:12 補充：
2.(3x y)-(2x-2y-3z)=3x-2x y-2y-3z=(3-2)x (1-2)y-3z=x-y-3z應該係2.(3x y)-(2x-2y-3z)=3x-2x y 2y 3z=(3-2)x (1 2)y 3z=x 3y 3z

1. a+a+2b-3b-c
= 2a-b-c
2. 3x-2x+y+2y+3z
=x+3y+3z
3. 6p+4q-5q+4r
=6p-q+4r
4. 5x-8x+7y+6y+3z
=-3x+13y+3z