y的2次方加3y减1等于0
∴y+3-1/y=0
y-1/y=-3
y的4次方减y的2次方加y的4次方分之1减y的2次方分之1减6
=y^4+1/y^4-(y²+1/y²)-6
=[(y²+1/y²)²-2]-(y²+1/y²)-6
=[(y-1/y)²+2]²-2-[(y-1/y)²+2]-6
=(9+2)²-2-(9+2)-6
=121-2-11-6
=102