F.1 maths.

a) put (0, -6) into ax - y + c = 0
a(0) - (-6) + c = 0
0 + 6 + c = 0
c = -6

b) put P(3 ,6) and c=-6 into ax - y +c = 0
a(3) - 6 + (-6) = 0
3a - 12 = 0
3a = 12
a = 4

c) put Q (q, q) , a=4 and c = -6 in ax - y + c = 0
4q - q + (-6) = 0
3q -6 = 0
3q = 6
q = 2
therefore coordinates of Q is (2, 2)

a.sub(0,-6):6+c=0
c=-6

b.sub P into ax-y-6=0
3a-6-6=0
a=4

c.sub Q into 4x-y-6=0
4q-q-6=0
q=2

so Q=(2,2)