7fc389…: “On a maroon square”

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Suppose that $f(x,y) =e^{8x+y^2-1}$ . Find $D_{\uvec {u}} f(-1,3)$ , where $\uvec {u}$ is a parallel to the line $5x+2y=1$ and points in the negative $y$ -direction. $D_{\uvec {u}}f(-1,3) = \answer {-\frac {14}{\sqrt {29}}}.$

From this, we see that at $(-1,3)$ , $f(x,y)$ initially in the $\uvec {u}$ -direction.

$\grad {f}(-1,3) = \vector {\answer {8},\answer {6}}$ and $\uvec {u}= \vector {\answer {\frac {2}{\sqrt {29}} } , \answer {\frac {-5}{\sqrt {29}} } }$