使用余式定理解决x^4+2x^3-3x^2-4x+4
问题描述:
使用余式定理解决
x^4+2x^3-3x^2-4x+4
答
x⁴+2x³-3x²-4x+4
=x²(x²+2x-3)-(4x-4)
=x²(x+3)(x-1)-4(x-1)
=(x-1)[x²(x+3)-4]
=(x-1)(x³+3x²-4)
=(x-1)[(x³-1)+(3x²-3)]
=(x-1)[(x-1)(x²+x+1)+3(x²-1)]
=(x-1)[(x-1)(x²+x+1)+3(x+1)(x-1)]
=(x-1)(x-1)[(x²+x+1)+3(x+1)]
=(x-1)²(x²+x+1+3x+3)
=(x-1)²(x²+4x+4)
=(x-1)²(x+2)²
答
设f(x)=x^4+2x^3-3x^2-4x+4 f(1)=0 ∴有因式x-1 f(x)=(x-1)(x^3+3x^2-4) 设:g(x)=x^3+3x^2-4 g(1)=0 ∴有因式x-1 g(x)=(x-1)(x^2+4x+4) =(x-1)·(x+2)^2 ∴f(x)=(x-1)^2·(x...