Open the math book with a smile and see that the product of two page numbers (between industry codes) is 420. What are the page numbers of these two pages?
Solution: Let the page numbers of these two pages be A and a+ 1 respectively.
a*(a+ 1)=420
a^2+a-420=0
(a+2 1)*(a-20)=0
A+2 1=0 a=-2 1 (S)
a-20=0 a=20
a+ 1=2 1
A: The page numbers of these two pages are 20 and 2 1 respectively.