✔ 最佳答案
1.設x^2-x+1=0,求(1+x^4)/x^26為?
Sol
x^2-x+1=0
(x+1)(x^2-x+1)=0
x^3+1=0
x^3=-1
1+x^4=1-x=-x^2
x^26=x^24*x^2=x^2
(1+x^4)/x^26
=(-x^2)/x^2
=-1
2. (x^2+x+1)/(x-1)^3=A/(x-1)+B/(x-1)^2+C/(x-1)^3,A+B+C=?
Sol
(x^2+x+1)/(x-1)^3=A/(x-1)+B/(x-1)^2+C/(x-1)^3
x^2+x+1=A(x-1)^2+B(x-1)+C
when x=2
4+2+1=A+B+C=7
請說明為何以連續綜合除法可得到結論
x^2+x+1=A(x-1)^2+B(x-1)+C
綜合除法可得到A=1
3x=B(x-1)+C
綜合除法可得到B=3
C=3
3.設abc不等於0,a+b+c=0,a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)=?
Sol
a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a(1/a+1/b+1/c)+b(1/c+1/a+1/b)+c(1/a+1/b+1/c)-3
=(a+b+c)(1/a+1/b+1/c)-3
=-3