Answer:
42 cm
Explanation:
We can solve the problem by using the lens/mirror equation:
[tex]\frac{1}{f}=\frac{1}{p}+\frac{1}{q}[/tex]
where
f is the focal length of the mirror
p is the distance of the object from the mirror
q is the distance of the image from the mirror
In this problem, we have
f = +14 cm is the focal length of the mirror (positive for a concave mirror)
p = 21 cm is the distance of the object
Solving for q, we find the distance of the image:
[tex]\frac{1}{q}=\frac{1}{f}-\frac{1}{p}=\frac{1}{14}-\frac{1}{21}=0.0238 cm^{-1}\\q=\frac{1}{0.0238}=42 cm[/tex]
