Question

A line passes through (1,1), (-2,4) and (6,n)

Answer 1

find sloope

for points (x1,y1) and (x2,y2)
slope=(y2-y1)/(x2-x1)

(1,1) and (-2,4)
slope=(4-1)/(-2-1)=3/-3=-1

so
for (1,1) and (6,n)
-1=(n-1)/(6-1)
-1=(n-1)/5
times both sides by 5
-5=n-1
add 1 to both sides
-4=n

the other pont is (6,-4)