2 0 1 6 x 3 + 2 0 1 5 x 2 + 2 0 1 4 x + 2 0 1 6 = 0
Let α , β and γ be the roots of the equation above .
Find the value of :
2 0 1 6 ( α 3 − β 3 − γ 3 ) + 2 0 1 5 ( α 2 − β 2 − γ 2 ) + 2 0 1 4 ( α − β − γ ) 2 0 1 6 ( α 3 + β 3 + γ 3 ) + 2 0 1 5 ( α 2 + β 2 + γ 2 ) + 2 0 1 4 ( α + β + γ )
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Nice solution! :)
Relevant wiki: Vieta's Formula - Higher Degrees
Since 2 0 1 6 x 3 + 2 0 1 5 x 2 + 2 0 1 4 x + 2 0 1 6 = 0 ⟹ 2 0 1 6 x 3 + 2 0 1 5 x 2 + 2 0 1 4 x = − 2 0 1 6 . And since α , β and γ are the roots of the equation, then we have:
⎩ ⎪ ⎨ ⎪ ⎧ 2 0 1 6 α 3 + 2 0 1 5 α 2 + 2 0 1 4 α = − 2 0 1 6 2 0 1 6 β 3 + 2 0 1 5 β 2 + 2 0 1 4 β = − 2 0 1 6 2 0 1 6 γ 3 + 2 0 1 5 γ 2 + 2 0 1 4 γ = − 2 0 1 6
Therefore,
2 0 1 6 ( α 3 − β 3 − γ 3 ) + 2 0 1 5 ( α 2 − β 2 − γ 2 ) + 2 0 1 4 ( α − β − γ ) 2 0 1 6 ( α 3 + β 3 + γ 3 ) + 2 0 1 5 ( α 2 + β 2 + γ 2 ) + 2 0 1 4 ( α + β + γ ) = − 2 0 1 6 + 2 0 1 6 + 2 0 1 6 − 2 0 1 6 − 2 0 1 6 − 2 0 1 6 = − 3
Nice one sir
⎩ ⎪ ⎨ ⎪ ⎧ 2 0 1 6 α 3 + 2 0 1 5 α 2 + 2 0 1 4 α + 2 0 1 6 = 0 2 0 1 6 β 3 + 2 0 1 5 β 2 + 2 0 1 4 β + 2 0 1 6 = 0 2 0 1 6 γ 3 + 2 0 1 5 γ 2 + 2 0 1 4 γ + 2 0 1 6 = 0
⎩ ⎪ ⎨ ⎪ ⎧ 2 0 1 6 α 3 + 2 0 1 5 α 2 + 2 0 1 4 α = − 2 0 1 6 2 0 1 6 β 3 + 2 0 1 5 β 2 + 2 0 1 4 β = − 2 0 1 6 2 0 1 6 γ 3 + 2 0 1 5 γ 2 + 2 0 1 4 γ = − 2 0 1 6
2 0 1 6 ( α 3 − β 3 − γ 3 ) + 2 0 1 5 ( α 2 − β 2 − γ 2 ) + 2 0 1 4 ( α − β − γ ) 2 0 1 6 ( α 3 + β 3 + γ 3 ) + 2 0 1 5 ( α 2 + β 2 + γ 2 ) + 2 0 1 4 ( α + β + γ )
= ( − 2 0 1 6 ) − ( − 2 0 1 6 ) × 2 ( − 2 0 1 6 ) × 3
= − 2 0 1 6 6 0 4 8
= − 3
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Relevant wiki: Vieta's Formula - Higher Degrees
Since α , β , γ are roots if the given equation, hence:
2 0 1 6 α 3 + 2 0 1 5 α 2 + 2 0 1 4 α = − 2 0 1 6 . . . ( 1 )
2 0 1 6 β 3 + 2 0 1 5 β 2 + 2 0 1 4 β = − 2 0 1 6 . . . ( 2 )
2 0 1 6 γ 3 + 2 0 1 5 γ 2 + 2 0 1 4 γ = − 2 0 1 6 . . . ( 3 )
LHS of ( 1 ) + ( 2 ) + ( 3 ) gives the numerator while LHS of ( 1 ) − ( 2 ) − ( 3 ) gives the denominator , hence answer is:
− ( 2 0 1 6 − 2 0 1 6 − 2 0 1 6 ) − ( 2 0 1 6 + 2 0 1 6 + 2 0 1 6 ) = − 3