Question

factorise y^4 - y^2 - y + y^3​

Answer 1

y⁴-y²-y+y³

= y⁴+y³-y²-y

= y²(y²+y)-1(y²+y)

= (y²+y) (y²-1)

= y(y+1) (y+1) (y-1) [a²-b² = (a+b)(a-b)]