Answer: A
si, di, are expressed as negative and f is expressed as positive values.
Explanation:
When the object is located at a location in front of the focal point of a convex len, the image will always be located somewhere on the same side of the lens as the object. The image is located behind the object. In this case, the image will be an upright image and the image is enlarged
In this question, the relationship between the focal length, image distance di and object distance is
I/f = 1/di + 1/do that is
I/f - 1/di - 1/do = 0
The image size si is also negative since the image is a virtual image.
Therefore, si, di, are expressed as negative, f is expressed as positive values.
Answer:
The value is 
Explanation:
From the question we are told that
The speed of the airplane from the north is 
The negative sign is because the direction is towards the south
The speed of the airplane from the east is 
The negative sign is because the direction is towards the west
The distance of the southbound plane from the airport is 
The distance of the westbound plane is 
Generally the distance between the plane is mathematically represented using Pythagoras theorem as

Next differentiate implicitly this equation to obtain the rate at which the distance between the planes changes
So

Here

=> 
=> 
=> 

=> 
=> 
The best place to put PFDs while you are out on your boat is at the top deck of your boat. PFDs must be placed at an area where it is easily accessible, especially in times of accidents, without any unnecessary gear or objects covering the PFDs, but it is best to wear a life jacket during the whole duration of the boat trip.
We have to calculate how many square feet a school custodian has to wax and to choose the correct answer. A gymnasium floor is in the shape of the square ( 20 by 20 feet ). The area of the square is : A = L^2. For L = 20 ft, A = 20^2 = 20 * 20 = 400 ft^2. Answer: <span>D. 400 square feet.</span>