Question

efetue a) (2+3i)(4+i) b) (2-3i)(4-i) C) (2-3i)(2+3i) d) (1+i)(1-i)

Answer 1

a)
$(2+3i)(4+i)= \\ 8+2i+12i+3i^2= \\ 8+12i+3(-1)= \\ 8+12i-3= \\ 5+14i$

-------------------------------
b)
$(2-3i)(4-i)= \\ 8-2i-12i+3i^2= \\ 8-14i+3(-1)= \\ 8-14i-3= \\ 5-14i$

--------------------------------------
c)
$(2-3i)(2+3i)= \\ 4+6i-6i-9i^2= \\ 4-9(-1)= \\ 4+9= \\ 13$

--------------------------------------
d)
$(1+i)(1-i)= \\ 1-i+i-i^2= \\ 1-(-1)= \\ 1+1= \\ 2$