The product of two numbers is 450. the first number is half the second number. which equation can be used to find x, the greater number?

The larger number is x/2 and the larger number is x.  We are told that the product of x and x/2 is 450.

x(x/2)=450

(x^2)/2=450

x^2=900

x=√900

x=±30

We were not told that the numbers must be positive so there are two solutions.  The larger number is either -30 or +30.

check...

-30(-15)=450  and 30(15)=450