a+b+c=9, a2+b2+c2=29 হলে, ab+bc+ca এর মান কত?
A
52
B
46
C
26
D
22
Correct Answer: 26
a + b + c = 9, a² + b² + c² = 29, ab + bc + ca = ? (a + b + c)² = a² + b² + c² + 2(ab + bc + ca) বা, ab + bc + ca = {(a + b + c)² - (a² + b² + c² )}/2 = (81 - 29) / 2 = 26