# Quadratic Inequality

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• April 8th 2011, 08:10 AM
Ilsa
Quadratic Inequality
Find the range of values of $k$ if $kx^2 + 8x > 6 - k$ for all real values of $x$.

The answer given is k > 8.
• April 8th 2011, 08:58 AM
Sambit
Find its discriminant and solve the equation discriminant=0 for k; then take a value of k which (i) is smaller than the smaller root, (ii) is higher than the higher root and (iii) lies between the two roots. Take that region which satisfies the equation you mentioned.
• April 8th 2011, 09:23 AM
Ilsa
I am getting the answer as k > -2 or k > 8. Why is only k > 8 specified in the answer?
• April 8th 2011, 10:27 AM
HallsofIvy
You have two errors: you get x> 2 (not -2) and x> 8 (not or). In order that both of those be true, x must be greater than 8.