Math IGCSE questions. Inversely proportional

Given that y is inversely proportional to x2 (X squared), and that y=2 when x=5.
a) Find an expression for y in terms of x
b) calculate i) the value of y when x=2
ii) a value of x when y=0.5

Thanks :) i completely forget how to do this

If y is directly proportional to x, y increases as x increases. If y is inversely proportional, y decreases as x increases.

A directly proportional relationship looks like this:

y = k*x

where k is come constant. Inversely proportional quantities will look like this:

y = k / x

So if y is inversely proportional to x², you'll have y = k / x². What is k? You can solve for it from the values you're given.

2 = k / (5)²

k = 50

y = 50 / x²

To find the answers to b and c, just plug in the given values.