We can start with the first two sets
(x+3i)(x-3i) = x²-9i² then simplify it to x²+9
multiply the next two
(x+1)(x-1) = x²-1
then multiply those two together
(x²+9)(x²-1) = x∧4-x²+9x²-9
combine like terms x∧4+8²-9
that is your answer
D: -4x^2 has the narrowest graph
Answer:
Speed of boat in still water is 6km/h
Speed of current is 4km/h
Step-by-step explanation:
We know speed = distance / time
Let the speed of boat in still water be x
Let the speed of current be y
Hence the speed of boat, down stream = 
Distance downstream = 20km
Time taken = 2 hours
We have

......(1)
Speed of boat upstream = 
Distance upstream = 4
Time taken = 2
We have

...(2)
Adding (1) & (2)


Substituting in (1) we get
