Question

The product of two integers is 72. One number is two less than five times the other. Which of the following equations could be used to find one of the numbers?

A. 2x2 - 5 = 72

B. 2x2 - 5x = 72

C. 5x2 - 2x = 72

D. 5x2 - 2 = 72

For plato users the answer is C

Answer 1

Let the 2 integers be x and y.

Their product is 72, so we write: xy=72. (I)

One of them, say y, is 2 less than 5 times the other. We can write this as the equation:
y=5x-2. (II)

To find one of numbers, say x, we can substitute y with 5x-2, in the first equation:

xy=72,


`x(5x-2)=72,`

expanding the left hand side expression we get:


`5x^2-2x=72`.


Answer: C