Explanation:
inversely proportional to x² means
y = k/x²
directly proportional would have meant
y = kx²
so, based on
y = k/x²
we need to find k out of the given data points, so that we can calculate autobahn data points.
let's start with x = 1
16 = k/1² = k
let's verify : x = 2
4 = 16/2² = 16/4 = 4 correct
x = 3
16/9 = 16/3² = 16/9 correct
x = 4
1 = 16/4² = 16/16 correct
a)
y = 16/x²
b)
y = 25
25 = 16/x²
25x² = 16
let's pull the square root on both sides
5x = 4
x = 4/5
FYI : x could have been also -4/5 (remember, any square root has a positive and negative number solution, as the square is the same). but the request was for the positive number.