To convert a number into scientific notation, we need to express it in the form of 'a x 10^n', where 'a' is a number greater than or equal to 1 and less than 10, and 'n' is an integer. In this case, we start with 450 x 10^4. First, we convert 450 into scientific notation. We can write 450 as 4.50 x 10^2. Now, we combine this with the 10^4 from the original expression. This gives us 4.50 x 10^(2+4) = 4.50 x 10^6. Thus, the correct scientific notation is 4.50 x 10^6.