1.

The entire graph of the equation `y=x^2+k x-x+9`in strictly above the `x-a xi s`if and only if`k

Answer» Correct Answer - `-5 lt k lt 7`
`y=x^(2)+(k-1)x+9=(x+(k-1)/(2))^(2)+9-((k-1)/(2))^(2)`
For entire graph to be above x-axis, we should have
`9-((k-1)/(2))^(2) gt 0`
`implies k^(2)-2k-35 lt 0`
`implies (k-7)(k+5) lt 0`
`implies -5 lt k lt 7`


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