If a + b = 10 and ab = 21, find the value of a3 + b3.

1.	If a + b = 10 and ab = 21, find the value of a3 + b3.
Answer» Given, a + b = 10, ab = 21 Choose a + b = 10 Cubing both sides, (a + b)³= (10)³ a³ + b³ + 3ab(a + b) = 1000 a³ + b³ + 3 x 21 x 10 = 1000 a³ + b³ + 630 = 1000 a³ + b³ = 1000 – 630 a³ + b³ = 370

Answer»

Given,

a + b = 10, ab = 21

Choose a + b = 10

Cubing both sides,

(a + b)³= (10)³

a³ + b³ + 3ab(a + b) = 1000

a³ + b³ + 3 x 21 x 10 = 1000

a³ + b³ + 630 = 1000

a³ + b³ = 1000 – 630

a³ + b³ = 370

Discussion

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