Question

If a+b=8 and ab=6, find the value of a³+b³.

Answer 1

Given : a + b = 8 and ab = 6

To find : value of  a³ + b³

 

Solution :  

 

By using the identity, (a + b)³ = a³ + b³ + 3ab(a + b)  

 

On cubing a + b = 8 both sides,  

(a + b)³ = 8³

(a)³ + (b)³ + 3(a )(b) (a + b) = 512

a³ + b³ + 3ab(a + b) = 512

a³ + b³ + 3 x 6 (8) = 512

[a + b = 8 and ab = 6 ]

a³ + b³ + 3 x 6 (8) = 512

a³ + b³ + 144 = 512

a³ + b³ = 512 - 144

a³ + b³ = 368

Hence the value of  a³ + b³ is 368.

HOPE THIS ANSWER WILL HELP YOU…..

 

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Answer 2

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