In an AP, the first term is x and the sum of the first n terms is zero. What is the sum of next m terms ?

Consider the following statements :

1. (25)! + 1 is divisible by 26

2. (6)! + 1 is divisible by 7

Which of the above statements is/are correct ? 

If z is a complex number such that $\frac{z-1}{z+1}$ is purely imaginary, then what is |z| equal to ? 

How many real numbers satisfy the equation |x - 4| + |x - 7| = 15 ?