To find the vertex of the quadratic function \( f(x) = - (x + 1.4)^2 + 6 \), we note that it is written in vertex form, which is \( f(x) = a(x - h)^2 + k \), where \((h, k)\) is the vertex.
In this case, we can identify:
- \( h = -1.4 \) (note that it is \( x + 1.4 \), which means \( h \) is negative)
- \( k = 6 \)
Therefore, the vertex of the function \( f(x) \) is \((-1.4, 6)\).
Answer: \((-1.4, 6)\)