Centroid of a Triangle

Centroid of a triangle, whose vertices are $\left(-a,0\right),\left(0,b\right) \text{and} \left(a,0\right)$ is _____

Find the centroid of the triangle, whose vertices are $\left(-4, 4\right), \left(-2, 2\right) \mathrm{and} \left(-6, 6\right)$.