Question 1041715
Concave to the left, and axis of symmetry is the x-axis.  Some equation of parabola {{{x=a(y-0)^2-10}}}  or as {{{x=ay^2-10}}}.  You do not know the value of a but you only know {{{a<0}}}.


Latus Rectum of 1 and the sign of a means that the focus is to the LEFT of the vertex.  Both focus AND vertex are on the axis of symmetry, so x=0, and y=1/2 for the point  (0, 1/2) as a endpoint for the latus rectum.  Other endpoint is (0, -1/2 ).


Using either endpoint for the latus recturm,  {{{0=a(1/2)^2-10}}} with the values substituted, and you can calculate and pick the correct value for "a".