Problem
The first three terms of a geometric sequence are as follows. \[ -5,20,-80 \] Find the next two terms of this sequence. Give exact values (not decimal approximations).
Solution
Step 1 ：\(r = \frac{20}{-5} = -4\)
Step 2 ：\(a_4 = a_3 * r = -80 * -4 = 320 \)
Step 3 ：\(a_5 = a_4 * r = 320 * -4 = -1280 \)
