X^4-5X^2+4/X^4-X^3-2^2 约分

问题描述:

X^4-5X^2+4/X^4-X^3-2^2 约分

(X^4-5X^2+4)/(X^4-X^3-2X^2)
=(X^2-1)(X^2-4)/[X^2(X^2-X-2)]
=(X-1)(X+1)(X+2)(X-2)/[X^2(X-2)(X+1)]
=(X-1)(X+2)/(X^2).