（x²-3x+1）分之x=1
x分之（x²-3x+1）=1
x-3+1/x=1
x+1/x=4
所以
（x⁴-9x²+1）分之x²
=（x²-9+1/x²）分之1
=【(x+1/x)²-11】分之1
=【16-11】分之1
=5分之1