Question

If area of triangle is 15 and coordinates are 1,k 4,-3 and -9,7 what is value of k

Answer 1

area of triangle = 1/2 [x₁(y₂ - y₃) + x₂(y₃ - y₁) + x₃(y₁ - y₂)]

15 = 1/2 [1(-3 - 7) + 4( 7 - k) -9 (k +3)]

15 × 2 = [-10 + 28 - 4k - 9k - 27]

30 = [- 9 - 13k]

30 = 9 + 13k

30 - 9 = 13k

21 = 13k

⇒ k = 21/13