# Which is the quadratic variation equation for the relationship given y varies directly with x^2 and y = 36 when x = 3?

Jun 29, 2016

$y = 4 {x}^{2}$

#### Explanation:

As $y$ varies directly with ${x}^{2}$, we can write this as

$y = a {x}^{2}$

Now we have $y = 36$ when $x = 3$, hence

$36 = a \times {3}^{2}$ or $9 a = 36$ or $a = \frac{36}{9} = 4$

and hence relation is $y = 4 {x}^{2}$