Solve problem.

Telephoto lens. find
the image distance i for an object that is 2,000,000 mm from
a 250-mm telephoto lens.

tel formula is 1/f=1/o + 1/i

1/250=1/2,000,000 + 1/i
5i(1/250)=(1/2,000,000 + 1/i)5i
1/50i = 5i/400,000i + 5i/5i
1/10i = 5i/80,000i + 5i/5i

I=8,000
Is this right?

1/250=1/2,000,000 + 1/i agree

I like powers of ten
10^-2 / 2.5 = 10^-6 / 2 +1/i

(2/2.5)10-2 = 10^-6 + 2/i

(2/2.5) 10^4 = 1 + 2*10^6 / i

8*10^3 = 1 + 2*10^6/i
8000 i = i + 2*10^6
7999 i = 2*10^6
i = 2,000,000/7999
i = 250 mm
In other words the object is effectively at infinity and its image is effectively at the focal point.

To solve this problem, we can use the telephoto lens formula 1/f = 1/o + 1/i, where f is the focal length, o is the object distance, and i is the image distance.

Given:
Object distance (o) = 2,000,000 mm
Focal length (f) = 250 mm

Substituting these values into the formula:
1/250 = 1/2,000,000 + 1/i

To solve for i, we can find a common denominator and simplify the equation.

Multiplying each term by 2,000,000*i (the common denominator):
2,000,000*i/250 = 2,000,000*i/2,000,000 + 2,000,000*i/i

Simplifying the equation:
8,000*i = 2,000 + 2,000,000

Combining like terms:
8,000*i = 2,002,000

Dividing both sides of the equation by 8,000:
i = 2,002,000 / 8,000
i = 250.25

Therefore, the image distance (i) for an object that is 2,000,000 mm away from a 250-mm telephoto lens is approximately 250.25 mm.

In your answer, you rounded down to 8,000, which is not accurate. The correct answer is approximately 250.25 mm.