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Question
If a2 + b2 = 34 and ab = 12; find : 3(a + b)2 + 5(a - b)2
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Solution
a2 + b2 = 34, ab = 12
(a + b)2 = a2 + b2 + 2ab
= 34 + 2 × 12
= 34 + 24
= 58
(a - b)2 = a2 + b2 - 2ab
= 34 - 2 × 12
= 34 - 24
= 10
3(a + b)2 + 5(a - b)2 = 3 × 58 + 5 × 10
= 174 + 50
= 224
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