Question

a + b = 8, ab = 15 then a3 + b3 =​

Answer 1

Answer:

152

Step-by-step explanation:

=> $a^3 + b^3 = (a+b)(a^2 + b^2 - ab)$

=>  $a^3 + b^3 = (a+b) [(a+b)^2 -2ab - ab]$

$[a^2 + b^2 = (a+b)^2 -2ab]$

=>  $a^3 + b^3 = (a+b) [(a+b)^2 - 3ab]$———————(1)

a + b = 8, ab = 15. Putting them in (1)

=> $a^3 + b^3 = (8) [(8)^2 -3(15)]$

=> $a^3 + b^3 = 8 (64-45)$

=> $a^3 + b^3 = 8*19$

=> $a^3 + b^3 = 152$

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