Question 363820
P(-2,3),Q(1,q) and R(7,0) collinear if PQ proportional to PR (other possibilities exist) : 
 
PQ = (1-(-2), q-3) = (3, q-3) PR = (9, -3)
 
we have : PR shall be 3 * PQ (with the x component), hence the y component of PQ has to be : -3/3 = -1, hence q = 2

QR = (6, -2)

PQ/QR is hence 3/6 = 1/2