410/20 * 75 = 1537.5 miles.
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.
Answer:
25
Step-by-step explanation:
Answer:
C. 24
Step-by-step explanation:
by algebra:
let "?" be x
35/30 = 28 / x (multiply both sides by 30)
35 = (28/x) (30) (multiply both sides by x)
35x = (28)(30)
35x = 840 (divide both sides by 35)
x = 840 / 35
x = 24
