What were the page numbers?

Question

Peter opened his book and found that the product of the page numbers for two facing pages was 156. What were the page numbers? 

Answer 1

Let the first page be numbeed x, then the next page must be numbered x+1.

 

So x(x+1) = 156.

 

A quadratic equation...can you solve it now?

Answer 2

Let n be the page on the left, then the page on the right would be n+1

 

Their product is n(n + 1) = 156

 

n² + n -156 =0

(n - 12)(n + 13) = 0

 

Then n = 12 or -13.

But a page number cannot be negative, so the pages are 12 and 13.