Let r be a root of the equation x2+ 2x + 6 = 0. The value of (r + 2) (r + 3) (r + 4) (r + 5) is equal to.
-126
r be a root ⇒r2 + 2r + 6 = 0 ...................(1)
now (r+2) (r+3) (r+4) (r+5)
= (r2 + 5r +6) (r2+ 9r + 20)
= (3r) (7r + 14) using (i)
= 21 (r2+ 2r)
= -126 using (i)