Question

Point A (1 , -5) is mapped as A' on rflection in the line y = 1. The point B (-5 , 1) is mapped as B' on reflection in the line y = 4. Write the co-ordinaes of A' and B' . Calculate AB'.

Answer 1

A (1 , -5) , he co-ordinate of A' = (1 , 2 × 1 - (- 5)) = (1 , 7)

B (-5 , 1) , the co-ordinate of B' = (-5 , 2 × 4 - (1)) = (-5 , 7)

The distance AB' = `sqrt ((-5-1)^2 + (7 - (-5))^2)`

=`sqrt ((-6)^2 + 12^2)`

= `sqrt (36 + 144)`

= `sqrt 180`

= 13.41 units