C3: Functions (Range&Domain)

The function f(x)= x^2-25 has domain (-∞,∞)
The function g(x)=2x-3 has domain (0,∞)

What is the domain and range of fg?
So I have the domain of fg which is (0,∞) but I don't get why on the markscheme the range is (-25,∞)

Domian of f is (0,∞) and the range of g is (-3,∞) which means we have to put the range of g into the function of f to get the range as it's the smallest...
but because it's a curve shaped graph, it's not (-16,∞) so I don't really know what to do.. Please help! Thanks.