Let's call the three points A (-4,5), B (4,5) and C (-3,-4). We have a triangle ABC and we need to calculate the perimeter. In other words AB+BC+CA. AB has length 4-(-4)=8. A and B have the same y value.
To find BC we use Pythagoras: BC^2=(5-(-4))^2+(4-(-3))^2=81+49=130. BC=sqrt(130).
To find AC: AC^2=(5-(-4))^2+(-3-(-4))^2=81+1=82. AC=sqrt(82).
Perimeter=8+sqrt(130)+sqrt(82)=28.5 approx.