What is 9867 rounded to the nearest 1000

Write an equation of the line given the two points below (write your equation in slope-intercept form, y=mx+b): (-4, 4) and (6, -4)

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.