Question

The product of two numbers is 713. The first number is 9 more than the second number. Which equation can be used to find x, the greater number?

x(x − 9) = 713
x(x + 9) = 713
x2 − 9 = 713
x2 + 9 = 713

Answer 1

Let x = first number and y = second number.
The first statement is expressed as
x*y = 713
The second statement is expressed as
x = y + 9
To find x, use the second equation in terms of y, that is y = x - 9. Then substituting it to the first equation yields
x*(x - 9) = 713