(x的三次方分之1-x的平方分之1)·x-1分之x的三次方
=(1/x³-1/x²) × x³/(x-1)
=（1/x³-x/x³)× x³/(x-1)
=(1-x)/x³× x³/(x-1)
=-(x-1)/x³× x³/(x-1)
=-1
2-x分之x-x的平方+4x+4分之4-x的平方
=x/(2-x)-(4-x²)/(x²+4x+4)
=x/(2-x)-(2+x)(2-x)/(x+2)²
=x/(2-x)-(2-x)/(x+2)
=x(x+2)/(2-x)(x+2)-(2-x)(2-x)/(x+2)(2-x)
=[(x²+2x)-(4-4x+x²)]/(2-x)(x+2)
=(x²+2x-4+4x-x²)/(x+2)(2-x)
=(6x-4)/(x+2)(2-x)