Answer
$\frac{(70,175,392)}{\sqrt{189189}}$
Work Step by Step
We know that $ai+bj+ck=(a,b,c).$
We know that for a matrix
$
\left[\begin{array}{rrr}
a & b & c \\
d &e & f \\
g &h & i \\
\end{array} \right]
$
the determinant, $D=a(ei-fh)-b(di-fg)+c(dh-eg).$
A vector orthogonal to $u$ and $v$ is $u\times v$.
$u×v$ is the determinant of the matrix $\begin{bmatrix}
i& j & k \\
7& -14&5\\
14&28 &-15 \\
\end{bmatrix}
$
Thus $u×v=(70,175,392).$
And a unit vector parallel to this is: $\frac{u\times v}{|u\times v|}=\frac{(70,175,392)}{\sqrt{70^2+175^2+392^2}}=\frac{(70,175,396)}{\sqrt{189189}}$
