Answer:
The area of the two-dimensional cross section is 
Step-by-step explanation:
we know that
The two-dimensional cross section that is parallel to face ABC is a triangle congruent with the triangle ABC
Therefore
Calculate the area of triangle ABC

we have that
Triangles ABC and DEF are congruent
so


substitute

Answer:
18km/h
Step-by-step explanation:
if the riverboat is already going 15 km/h and the current is 3km/h then you should add and you get 18 km/h
If P <span>is the midpoint of DE then
DE = 2(DP)
10x - 12 = 2(3x + 2)
10x - 12 = 6x + 4
10x - 6x = 4 + 12
4x = 16
x = 16/4
x = 4
DP = 3x + 2 = 3 * 4 + 2 = 12 + 2 = 14 units</span>
Answer:
2x²-32 ⇒ x²=16⇒ (-4,4)
4x²-100 ⇒x²=25 ⇒(-5,5)
x²-55=9 ⇒x²=64 ⇒(-8,8)
x²-140=-19 ⇒x²=121 ⇒(-11,11)
2x²-18=0 ⇒x²=9 ⇒(-3,3)