(y3 - 5y2) ÷ y x (y - 1)
= (y3 ÷ y - 5y2 ÷ y) x (y - 1)
= (y(3-1) - 5y(2-1)) x (y - 1)
= (y2 - 5y1) x (y - 1)
= y2 x (y - 1) - 5y1 x (y - 1)
= y(2+1) - y2 - 5y(1+1) - 5y
= y3 - y2 - 5y2 - 5y
= y3 - 6y2 - 5y
Hence, (y3 - 5y2) ÷ y x (y - 1) = y3 - 6y2 - 5y