(- 5, - 6 ) or (- 5, 10 )
using the distance formula
d = √(x₂ - x₁ )² + (y₂ - y₁ )²
with (x₁, y₁ ) = (1, 2 ) and (x₂, y₂ ) = (- 5, y )
d = √(- 5 - 1 )² + (y - 2 )² = 10
d = √36 + (y - 2 )² = 10
square both sides
36 + (y - 2 )² = 100 ( subtract 36 from both sides )
(y - 2 )² = 64
take the square root of both sides
y - 2 = ± 8 ( add 2 to both sides )
y = 2 ± 8
y = 2 + 8 or y = 2 - 8 ⇒ y = 10 or y = - 6
coordinates of A = (- 5, - 6) or (- 5, 10 )
