Compute (1+i)(1+2i)(1+3i).
Expanding, gives us (1+i)(1+2i)=−1+3i. Then, expanding again gives us (−1+3i)(1+3i)=−10.
(1 + i)(1 + 2i)(1 + 3i)
= (1 + 2i - i) (1 + 2i + i) (1 + 2i)
= ((1 + 2i)^2 + 1)(1 + 2i)
= (-3 + 4i + 1)(1 + 2i)
= (-2 + 4i)(1 + 2i)
= -2(1 - 2i)(1 + 2i)
= -2 (5)
= -10