we have that
y=-3x²+5x+11
we know that
the equation of the parabola in standard form can be expressed in one of the following two ways
y=ax²+bx+c
the parabola opens up if a is positive and opens down if a is negative
and
x=ay²+by+c
the parabola opens right if a is positive and opens left if a is negative
in this problem
the equation is of the form
y=ax²+bx+c
a=-3
so
the parabola opens down
using a graph tool
see the attached figure
the vertex of a parabola is a maximum
the answer is
the parabola opens down