Answer
$$1.5, \ or, \ -1
.$$
Work Step by Step
For the equation $-2x^2 +x +3= 0$, we use the quadratic formula as follows
$$
x=\frac{-b \pm \sqrt{b^{2}-4 a c}}{2 a},
\\
a=-2, \quad b=1, \quad c=3
.$$
That is, $$ x=\frac{-1\pm \sqrt{1+24}}{2(-2) }=1.5, \ or, \ -1
.$$
