For all negative reals c , let α c and β c be the roots of the equation 2 x 2 + 6 x + c = 0 . What is the smallest integer that must be greater than
β c α c + α c β c ?
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Why must c be < 0
Ok, got it, it is given in the question
If one root b<0 then c (constant term )must be negative because the coefficient of X is positive hence another root a must be positive So a/b is negative.... Then by inequality "if x<0 then x+1/x<2" so a/b +b /a <2
How did you arrive to this inequality?
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I've edited your question for clarity. Can you review it for accuracy?
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thanks for reviewing this question is alright now.
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For simplicity in writing, I'm referring to the roots as α and β .
α + β = − 3 and α β = 2 c ,
So, β α + α β = α β α 2 + β 2 = α β ( α + β ) 2 − 2 α β = c 2 ( 9 − c ) = c 1 8 − 2
Consider y = c 1 8 − 2 which we have to maximize for c < 0 . It is the graph of a rectangular hyperbola in the fourth quadrant. After tracing the graph, you will find that the line y = − 2 is an asymptote to the curve and the curve lies entirely below it. Thus, the smallest integer greater than y is − 2