If the two roots of the quadratic $4x^2+7x+k$ are $\frac{-7\pm i\sqrt{15}}{8}$, what is $k$? , what is k?
\(f(x)=4x^2+7x+k \\ \text{has roots }x = \dfrac{-7\pm i\sqrt{15}}{8}\\ b^2-4ac=-15\\ 7^2 - 4(4)k = -15\\ -16k=-64\\ k=4\)
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