Jawabanmu

2014-08-25T16:57:06+07:00
1. 13a-8b+12a+9b
25a-b
2. 15i+14b+13k-30i-45j+51k
-15i-31b+64k
2014-08-25T16:59:09+07:00
(13a-8b)+(12a+9b)
= (13a+12a) + (-8b+9b)
= 25a + b

(15i+14b+13k ) +( -30i-45j+51k)
=(15i-30i ) + (13k +51k) +14b - 45j
= -15i + 64k + 14b + 45j