Question

If a+b=3& ab=2, what is the value of a3+b3

Answer 1

∆nswer

a+b = 3
: b = 3 - a
and ,
ab = 2
so , (3-a).a = 2
3a - a² = 2
a² - 3a + 2 = 0
(a-1)(a-2) = 0
a = 1,2
b = 2,1
Hence , a³ + b³ = 1³ + 2³ = 1 + 8 = 9

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Answer 2

#ur Ans
____________

Given that

a+b = 3

ab = 2

a^3 +b^3 = ?

Now

$= > ( a + b {)}^{3} = {a}^{3} + {b}^{3} + 3ab(a + b) \\ \\ now \: putting \: the \: value \\ \\ = > (3 {)}^{3} = {a}^{3} + {b}^{3} + 3 \times 2 \times (3) \\ \\ = > 27 = {a}^{3} + {b}^{3} + 18 \\ \\ = > {a}^{3} + {b}^{3} = 27 - 18 \\ \\ = > {a}^{3} + {b}^{3} = 9$


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