Question

If a+b=15 and ab=56 then the value of a cube +b cube /a square +b square

Answer 1

a + b = 15 and ab = 56

a³ + b³ = (a + b)³ - 3ab (a+b)
            = (15)³ - 3*56 (15)
            = 3375 - 2520
            = 855

a² + b² = (a + b)² - 2ab
            = (15)² - 2*56
            = 225 - 112
            = 113

Hope this helps you.

Answer 2

Hey!

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Given :-

a + b = 15

ab = 56

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Solution

According to the question

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a³ + b³ = (a + b)³ - 3ab . (a + b)

= (15)³ - 3 × 56 × 15

= 3375 - 2520

= 855

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Now

(a + b)² = (a + b)² - 2ab

= (15)² - 2 × 56

= 225 - 112

= 113

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Regards :)

Cybary

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