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Question
If a2 + b2 = 34 and ab = 12; find : 7(a - b)2 - 2(a + b)2
Solution
a2 + b2 = 34, ab= 12
(a + b)2 = a2 + b2 + 2ab
= 34 + 2 x 12 = 34 + 24 = 58
(a - b)2 = a2 + b2 - 2ab
= 34 - 2 x 12 = 34- 24 = 10\
7(a - b)2 - 2(a + b)2 = 7 x 10 - 2 x 58 = 70 - 116 = - 46
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