The answer is negative because, ( -81/-9) =(+9). -(+9) = -9. Maybe for got the - sign before the equation
5x + 20 = 70
5x = 70 - 20
5x = 50
x = 50/5
x = 10
5(10) + 20 = 70
50 + 20 = 70
70 = 70
hope this helps :)
Answer:
DL/dt = 17 mph
Step-by-step explanation:
The ships and the port shape a right triangle
Ship going west ( x-direction) is traveling at 15 mph
Ship going north (y-direction) is traveling at 10 mph
The distance L between ships is:
L² = x² + y²
Tacking derivatives on both sides of the equation with respect to time
we get
2*L*DL/dt = 2*x*Dx/dt + 2*y*Dy/dt (1)
In that equation we know:
Dx/dt = 15 mph
Dy/dt = 10 mph
At the moment ship traveling from the east is at 3 miles from the port
then x = 3 m and the other ship is at 4 miles north
then by Pythagoras theorem
L = √ 3² + 4² L = 5
By substitution in equation 1
2*5*DL/dt = 2*3*15 + 2*4*10
10* DL/dt = 90 + 80
DL/dt = 170 / 10
DL/dt = 17 mph
