First find the prime decomposition of 1575, then multiply by some prime numbers in order to make the final product a product of even powers of prime numbers...
smallest k such that 450*k is a perfect square.
In order to have an even (hence a square) power of 2, we have to multiply by 2.
In order to have an even power of 3, we have to multiply by 3.
There's no need to do it for 5, because it's already an even power.
So k=2*3=6 is the number we're looking for.
Now try to do it for 1575.