Given, ax2+bx+c=0 According to the question, a,b,c∈{1,2,3,4,5,6} ∴‌‌n(S)=6×6×6=216 For equal roots ‌D‌‌=0 ⇒‌b2−4ac‌‌=0 ⇒‌b2‌‌=4ac ⇒‌ac‌‌=‌
b2
4
b=2,ac=1⇒(a=1,c=1) b=4,ac=4⇒(a=1,c=4) or (a=4,c=1) (a=2,c=2) b=6,ac=9⇒(a=3,c=3)