According to cartesion sign convention, which mirror and which lens has negative focal length?

According to Cartesian sign convention, object distances (u) are always negative as the object is placed to the left of the mirror/lens.

• Focal length (f) is positive for a convex lens and convex mirror.

• Focal length is negative for concave lens and concave mirror.
Image distance (v) can be both positive and negative for convex lens and concave mirror depending on the position of the object.

• Image distance is always negative for a concave lens.

• Image distance is always positive for a convex mirror.