(i) (2x+1)5(2x+1)(3x+5)
=5(3x+1)
(ii) 13x(y−4)26xy(x+5)(y−4)
=13x(y−4)2×13×xy(x+5)(y−4)
=2y(x+5)
(iii) 104pq(q+r)(r+p) 52pqr(p+q)(q+r)(r+p)
= 2×2×2×13×p×q×(q+r)×(r+p)2 ×2×13×p×q×r×(p+q)×(q+r)×(r+p)
=21r(p+q)
(iv) 20(y+4)(y2+5y+3)
= 2×2×5×(y+4)(y2+5y+3)
= 5(y+4)20(y+4)(y2+5y+3)
= 5×(y+4)2×2 ×5(y+4)×(y2+5y+3)
= 4(y2+5y+3)
(v)x(x+1)x(x+1)(x+2)(x+3)
=x(x+1)x(x+1)(x+2)(x+3)
=(x+2)(x+3)