Question 884075
let x be the first whole number
x^2=x^2
let x+1 be the next whole number 
(x+1)^2=x^2+2x+1


(x+1)^2-x^2=31
x^2+2x+1-x^2=31

2x+1=31
2x=30
x=15
x+1=16
check
16^2=256
15^2=225
256-225=31

ok