Question

If (a + b)² = 10 and (a - b)² = 4 then what is a² +b²?

• A. 6
• B. 3
• C. 14
• D. 7

Answer 1

Answer:

D. 7

Given (a+b+c) = 13, a² + b² + c² = 69 We have, (a+b+c)² = a² +b²+c²+2 (ab+bc+ac) 13² = 69 +2 (ab+bc+ca) (ab+bc+ca) = (13² - 69)/2 = (169 - 69)/2 = 100/ 2 = 50