A luminous object and a screen are placed on an optimal bench and a converging lens is placed between them to throw a sharp image of the object on the screen. The linear magnification of the
image is found to be 2.5. The lens is now moved 30 cm, nearer the screen and a sharp image again
formed. Calculate the focal length of the lens.​

because it says use -2,0,and 2 for x, we can plug those numbers into the equation. y/4=3/4(-2)+2   y/4= -1 1/2 +2 now to get x by itself, we can multiply each side by 4. y=-6+8 which equals y=2 when x=-2. now you can do the same thing with 0 and 2 as x. you get y=8 when x=0 and y=14 when x=2.

x   |   y

-2 |   2

0   |   8

2   |   14

overcharge is the right answer system