(2-5i)(3+i)
use foil method to expand it into standard form
6+2i-15i+5i^2
5i^2-13i+6
Correct, c and e. they are the only ones that make sense
Answer:
Here's how I would do it.
Step-by-step explanation:
If two triangles are similar, corresponding sides are in the same ratio.
We know the measures of b and a, so we can calculate the ratio b/a.
d and b are in the same ratio, so
We know the measures of c, b, and a, so we can calculate the value of d.
Speed = Distance / Time
Distance = Speed*Time
For this problem, we should bear in mind that current speed has an impact on the boat speed...
for upstream, the boat goes against the current, and so its speed is
U = V - C
where V is the speed of the boat
C is the current speed
for downstream, it will be:
D = V + C
Convert the problem into mathematical equations:
4D + 3U = 116
3D + 4U = 108
4(V+C) + 3(V-C) = 116
4V + 4C + 3V -3C =116
7V + C = 116
3(V+C) + 4(V-C) = 108
3V + 3C + 4V - 4C = 108
7V - C = 108
Solving the equations:
7V + C = 116
7V - C = 108
14V = 224
V = 16km/hr —-> speed of boat
to get C:
7(16) + C = 116
C = 4km/hr
The value of the expression is 12
