Because the expressions x and y² varies inversely, the equation that can be used in order to relate them is,
y² = k/x
k here is the constant of proportionality. Using the first set of given, x = 4 and y = 10, we determine the value of the proportionality constant.
k = (x)(y²)
Substitute the known values to the equation,
k = (4)(10²) = 400
The completed equation for the relation is therefore,
y² = 400/x
Substituting the value of y to this equation,
(2²) = 400/x
The value of x is 100.
ANSWER: D. x = 100
