Q. 54.2( 32 Votes )

If area of triangle is 35 sq units with vertices (2, –6), (5, 4) and (k, 4). Then k is
A. 12

B. –2

C. –12, –2

D. 12, –2

Answer :

Given vertices of the triangle are (2, – 6), (5, 4) and (k, 4).

Let the vertices of the triangle be given by (x1, y1), (x2, y2), (x3, y3)


Area of triangle is given by Δ =


Given, Area of triangle = Δ = 35 sq. units


= 35


� 35 = 1/2 × [2 × (4 × 1 – 4 × 1) – (-6) × (5 × 1 – k × 1) + 1 × (5 × 4 – k × 4)]


� 35 = 1/2 × [2 × (4 – 4) + 6 × (5 – k) + 1 × (20 – 4k)]


� 35 × 2 = (2 × 0 + 30 – 6k + 20 – 4k)


� 70 = 30 – 6k + 20 – 4k


� 70 = 50 – 10k


70 – 50 = -10k and -70 – 50 = -10k


20 = -10k and -120 = -10k


k = -20/10 and k = 120/10


k = -2 and k = 12

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