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9 years, 7 months ago
determine the range of value of x for which x* -2x +5 /3x*-2x-5 is greater than 1/2?(here*means power2)
9 years, 7 months ago
$$x^2 - 2x + 5$$ > 0 for all x since discriminant < 0 and coefficient of x > 0
$$3x^2 - 2x - 5$$ > 0 for x < -1 or x > 5/3
In this range, the given inequality becomes $$2x^2 - 4x + 10 > 3x^2 - 2x - 5$$ => $$x^2 + 2x - 15 < 0$$ => -5 < x < 3
So, the intersection of these two ranges is -5 < x < -1 or 5/3 < x < 3
$$3x^2 - 2x - 5$$ < 0 for -1 < x < 5/3
In this range, the inequality becomes $$2x^2 - 4x + 10 < 3x^2 - 2x - 5$$ => $$x^2 + 2x - 15 > 0$$ => x < -5 or x > 3
The intersection of the two ranges is a null set.
So, the solution set is the range -5 < x < -1 or 5/3 < x < 3
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