Using long division method for expanding we get,
x−4+5x−5+18x−6+54x−7–––––––––––––––––––––––––––––––
x4−5x3+7x2+x−8)1
1−5x−1+7x−2+x−3−8x−4
(−)(+)(−)(−)(+)–––––––––––––––––––––––––––––––––––
5x−1−7x−2−x−3+8x−4
5x−1−25x−2+35x−3+5x−4−40x−5
(−)(+)(−)(−)(+)––––––––––––––––––––––––––––––––––––––––
18x−2−36x−3+3x−4+40x−5
18x−2−90x−3+126x−4+18x−5−144x−6
(−)(+)(−)(−)(+)––––––––––––––––––––––––––––––––––––––––––
54x−3−123x−4+22x−5+144x−6
54x−3−270x−4+378x−5+54x−6−432x−7
(−)(+)(−)(−)(+)–––––––––––––––––––––––––––––––––––––––––––––
147x−4−356x−5−90x−6−432x−7
Hence, remainder = 147x−4−356x−5+90x−6+432x−7