Math, asked by Madav, 1 year ago

Find the value of a3+8b3 if a+b=10 and ab=18

Answers

Answered by swapnil756
1
Hello friend

Given a + b = 10 and ab = 18

Consider, a3 + 8b3 = a3 + 8b3

    = (a + b)3 − 3 × a × b(a + b)  [Since, a3 + b3 = (a + b)− 3ab(a + b)]

    = (a + b)3 − 3ab(a + b)

    = (10)3 − 6 × 18 × 10

    = 1000 − 1080 = -80

Hope it helped u 

swapnil756: plzzz mark it as brainliest plzz
khushipawar: what a good knowledge
swapnil756: ur saying to whom
Madav: Swapnil did it incorrectly he told a+b=10 and during calculation did asva+2b=10
Madav: As a+2b=10
swapnil756: i have done it correctly'
swapnil756: that is 8b cube so it will be (2b)cube
swapnil756: so i m ryt
swapnil756: :((
Answered by Anonymous
4
Hello 

I think  a + 2b = 10 and ab = 18 
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 we know ,

a³ + b³ = ( a + b ) ³ - 3ab ( a+b ) 

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here 

a³ - (2b) ³ = (a + 2b ) ³ - 6ab ( a + 2b ) 
                =  10³   - 6 x 18 ( 10 ) 
                = 1000 -  1080 
                = -80 
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Madav: Thanks for helping me
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