✔ 最佳答案
我計到 a^3 - 2a^2 - 5a + 6
步驟如下:
(a+2)(a-1)(a-3)
= (a^2 + 2a - a - 2) (a - 3)
= (a^2 + a - 2) (a - 3)
= a^3 + a^2 - 2a - 3a^2 - 3a + 6
= a^3 + a^2 - 3a^2 - 2a - 3a + 6
= a^3 - 2a^2 - 5a + 6
2007-10-09 16:50:47 補充:
我先計頭兩項,再計第三項。逐步慢慢拆就應該岩。
2007-10-10 00:51:02 補充:
(a+2)(a-1)(a-3)= [a(a-1)+(2)(a-1)] (a-3) --- 先計頭兩項,所以加了一對引號 = (a^2-a+2a-2) (a-3)= (a^2+a-2) (a-3) ---把已拆了的頭兩項作加減而得出的姑果= a(a^2+a-2) - 3(a^2+a-2) --- 把(a-3)拆進前面的結果= a^3+a^2-2a-3a^2-3a+6= a^3+a^2-3a^2-2a-3a+6 --- 以次序排= a^3-2a^2-5a+6
2007-10-10 00:59:44 補充:
直式計法: (a 2)x (a-1)-------------- a^2 2a --- (a 2)(a)+) -a- 2 --- (a 2)(-1)---------------- a^2 a-2 --- 已把(a 2)(a-1)拆掉x (a-3)----------------a^3 a^2-2a --- (a^2 a-2)(a)+) -3a^2-3a 6 --- (a^2 a-2)(-3)----------------------a^3-2a^2-5a 6 = Answer