১.
যদি a + b + c= 9, ab + bc + ca= 31 হয়, তবে a² + b² + c²= কত?
ব্যাখ্যা
দেয়া আছে,
a + b + c = 9
ab + bc + ca = 31
আমরা জানি,
(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)
a2 + b2 + c2 = (a + b + c)2 - 2(ab + bc + ca)
= 92 - 2 × 31
= 81 - 62
= 19
a + b + c = 9
ab + bc + ca = 31
আমরা জানি,
(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)
a2 + b2 + c2 = (a + b + c)2 - 2(ab + bc + ca)
= 92 - 2 × 31
= 81 - 62
= 19