First, factor the denominator of the first term:
4y−y3=y(4−y2)=y(2−y)(2+y)=−y(y−2)(y+2) The expression becomes:
−y(y−2)(y+2)8+y+21−y1 Now, find a common denominator, which is −y(y−2)(y+2). Rewrite each term with the common denominator: −y(y−2)(y+2)8+(y+2)(−y(y−2))−y(y−2)−y(−1)(y−2)(y+2)−(y−2)(y+2) −y(y−2)(y+2)8+−y(y−2)(y+2)−y(y−2)−−y(y−2)(y+2)−(y2−4) Combine the numerators:
−y(y−2)(y+2)8−y(y−2)+(y2−4)=−y(y−2)(y+2)8−y2+2y+y2−4 Simplify the numerator:
−y(y−2)(y+2)4+2y=−y(y−2)(y+2)2(2+y) Cancel the common factor (y+2): −y(y−2)2=−y2+2y2=2y−y22