Question

a3+ b3

if a + b = 3, and ab =1 2.​

Answer 1

Step-by-step explanation:

a³+b³

=(a+b)³-3ab(a+b)

=(3)³-3×12×3

=27-108

=-81

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Answer 2

Step-by-step explanation:

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

here (a+b)^2= 9

=> a^2+b^2+ 2ab = 9

=> a^2+b^2= 9-2ab = 9-24 = -15

now (a+b)(a^2+b^2-ab) = (3)(-15-12) = (3)(-27)= - 81