Q.the image of the pt.(3,8) in the line x+3y=7.

options a.(1,4)

b.(4,1) c.(-1,-4)

d.(-4,-1)

[Ans: (c)]

Learn a formula

Reflection of a point P(x₁,y₁) in ax+by+c=0 is Q(h,k) where

 (h-x₁)/a = (k-y₁)/b = {-2(ax₁+by₁+c)}/(a²+b²)

now apply this formula...

(h-3)/1 = -40/10 = -4

or, h=-1

(k-8)/3 = -40/10 = -4

or, k = -4.

thus point of reflection is (-1,-4).