Question

fill in the missing term in the geometric sequence. -1, 4, -16, ____, -256

Answer 1

$a_1=-1;\ a_2=4;\ a_3=-16;\ a_4=?;\ a_5=-256\\\\a_3:a_2=r\to r=-16:4=-4\\\\a_4=a_3r\to a_4=-16\cdot(-4)=64\\\\Answer:\boxed{64}$