If you expand out the brackets you get this,
(4+5i)(a+2i) = 4a + (5a)i + 8i - 10
The -10 comes from 5i * 2i.
Squaring i becomes -1.
Let's group the real stuff together,
and imaginary separately,
(4a - 10) + (5a + 8)i
For this to be purely imaginary,
the real part needs to be zero.
Therefore 4a - 10 = 0
Solve for a.
7(3x/1)=-1
7(3x)=-1
21x=-1
21x/21=-1/21
X=-1/21
Answer: -1/21
Answer: $2
Step-by-step explanation:
just do 4 divided by 2 and your answer is 2
50 m/s is going to be 180 km/h or 3 km/s.
50 / 1000 = 0.05
0.05 x 60 = 3 kilometers a minute.
3 x 60 = 180 kilometers an hour.
50 m/s divided by 1 kilometer = 0.05 kilometers a second. You then multiply it by 60 to get it in minutes, and then 60 again to get it in hours. because their are 3600 seconds in an hour. So you could divide 50 meters per second by 1000 meters or 1 kilometer and then multiply it by 3600 seconds to get 180 kilometers an hour.
