Mathematics
If the sum of two numbers is 11 and sum of their cubes is 737, find the sum of their squares.
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Answer
Let two numbers be a and b then according to question,
a + b = 11 and a3 + b3 = 737.
Cubing both sides of a + b = 11,
⇒ (a + b)3 = (11)3
⇒ a3 + b3 + 3ab(a + b) = 1331
⇒ 737 + 3ab(11) = 1331
⇒ 33ab = 1331 - 737
⇒ 33ab = 594
⇒ ab = 18.
We know that,
a2 + b2 = (a + b)2 - 2ab
Substituting values we get,
⇒ a2 + b2 = (11)2 - 2(18) = 121 - 36 = 85.
Hence, sum of squares of two numbers = 85.
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