00:01
We'd like to find how long or how far the object is moved, and what is the focal length of the mirror.
00:07
So in our first case, we're given our magnification is twice, is two times as large.
00:14
So we have s1 prime over s1 equal to 2.
00:18
We can then find our focal length.
00:20
Our focal length is s1, s1, s1, divided by s1 plus s1 prime.
00:26
In our second case, we have s2 prime over s2 to be equal to 3.
00:31
Since it's magnified three times.
00:34
Now our mirror is moved to 75 centimeters so we can write s2 prime equal to s1 prime plus 75.
00:44
By this equation we can write another expression 2 s1 minus 3 s2 is equal to 75...