Need help trying to figure out

Through non-collinear points there is exactly one plane.

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

Does anyone know how to solve and graph this: 4 + | a + 2 | < 7the only part i don't get is the "4 +"