Question
If a + b = 5 and ab = 6, find a2 + b2.
A. 12
B. 13
C. 8
D. 16
Answer: B. 13
Solution:
(a+b)2 = a2 + b2 + 2ab
⇒ (5)2 = a2 + b2 + 2×6
⇒ 25 = a2 + b2 + 12
⇒ 25 − 12 = a2 + b2
⇒ 13 = a2+b2
∴ a2 + b2 = 13
Hence, The Answer a2 + b2 = 13.
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