Question

alisa

請問畫紅色底線的算式是怎麼來的

※範例7 因式定理推廣
(1) f(x) 為三次多項式,已知(1)=f(2)=f(3)=0,f(0)=12,則f(-1)之值,
(2) f(x) 為三次多項式,已知f(1)=f(2)=f(3)=-2,f(4)=10,則f(-1)之值
7 (1) f(1) = f(a) = f(3) = 0
得f(x)有因式(x-2,x-3
因f(x)為三次多項式,所以設f(x)=a(x-1)(x) (X-3)
2 fro) = -ba = 12,a=-2.所求f(-1)=(-)-(-2)(-3)(4)=48
得分攻略當場練

Answer 1

Ny-Ålesund

f(0) 即 x = 0 代入
f(0) = a(0-1)(0-2)(0-3) = 12