What is .645 converted into a fraction in simplest form

5× 1/2 = ? a) more than 5 because you are multiplying by a whole number b) 5/10 because you multiply the numerator and denominator by 5 c) less than 5 because you are multiplying by a number that is more than 1 d) less than 5 because you are multiplying by a number that is less than 1

If you could answer these your a life saver

Let f(x) = 5/x and g(x)=2x2+5x. what two numbers are not in the domain of f o g