Question

if a+b =9 ,a²+b²= 41 ab =20 then the value of a³+b³=?

Answer 1

a³+b³ = (a+b)(a²+b²-ab)
or, a³+b³ = 9.(41-20)
or, a³+b³ = 9.21
or, a³+b³ = 189

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Answer 2

(a+b) power 3 =a cube + b cube + 3ab (a+b) = 729

ab =20 a+b =9 so substitute it

then it will come a cube + b cube +60(9) = 729


a cube + b cube = 729 - 60(9)

a cube + b cube = 729 - 540 =》189