Question

Find two consecutive whole numbers whose product is 72.

Answer 1

$n(n+1)=72\\ n^2+n-72=0\\ n^2+9n-8n-72=0\\ n(n+9)-8(n+9)=0\\ (n-8)(n+9)=0\\ n=8 \vee n=-9\\\\ n+1=9 \vee n+1=-8$

8 and 9 or -9 and -8