Question

if a³+b³=28 , a+b=4 find the value of ab​

Answer 1

Given:

a³+b³  = 28 and a + b = 4

We have to find, the value of ab = ?

a + b = 4

Cubing both sides, we get

(a + b)³ = 4³

Using the algebraic identity,

(a + b)³ = a³+b³+3ab(a+b)

a³+b³+3ab(a+b) = 64

substitute a³+b³  = 28 and a + b = 4

We get,

⇒ 28 + 3ab(4) = 64

⇒ 12ab = 64 - 28 = 36

ab = 36/12

ab = 3

Hence the required ab value is 3

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