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Find the least value of a such that the function f given by `f(x)=x^2+a x+1`is strictly increasing on `(1, 2)dot`

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`f(x) = x^2+ax+1`
For `f(x)` to be strictly increasing, `f'(x) gt 0`.
`:. 2x+a gt 0`
`=> a gt -2x.` It is given that `x in (1,2)`.
`:. -2x in (-4,-2)`.
So, `a gt `Maximum value of `-2x`.
`:. a gt -2`.
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