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If a + b + c = 9 and ab + be + ca = 26, find a2 + b2 + c2 |
Answer» Given that a + b + c = 9 Squaring on both sides, (a + b + c)2 = 92 ⇒ a2 + b2 + c2 + 2 (ab + be + ca) = 81 ⇒ a2 + b2 + c2 = 81 – 2 (ab + be + ca) (by problem) = 81 – 2 x 26 = 81 – 52 = 29 |
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