Question

if a+b=4 ,ab=2 then a³ + b³ = ??

Answer 1

Answer:

40

Step-by-step explanation:

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

64 = a^3 + b^3 +24

Therefore,

a^3 + b^ 3 = 64 -24

= 40

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Answer 2

a³ + b³ = (a+b) ( a2 +b2 + ab)

a+b= 4 (given) ...

(a+b) ^2 = 8

a2 +b2 +2ab = 8

a2 +b2 = 9 + 2× 2

a2 +b2 = 13

a³ + b³ = ( 4) ( 13 + 2 )

a³ + b³ = 4× 15

a³ + b³ = 60........