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Mathematics

The sum of two whole numbers is 7 and the sum of their cubes is 133, find the sum of their squares.

Expansions

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Answer

Let two numbers be x and y.

Given,

The sum of two whole numbers is 7 and the sum of their cubes is 133.

x + y = 7 and x3 + y3 = 133

By formula,

⇒ x3 + y3 = (x + y)3 - 3xy(x + y)

⇒ 133 = 73 - 3xy × 7

⇒ 133 = 343 - 21xy

⇒ 21xy = 343 - 133

⇒ 21xy = 210

⇒ xy = 10.

By formula,

⇒ (x + y)2 = x2 + y2 + 2xy

⇒ 72 = x2 + y2 + 2 × 10

⇒ 49 = x2 + y2 + 20

⇒ x2 + y2 = 49 - 20

⇒ x2 + y2 = 29.

Hence, sum of squares of numbers = 29.

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