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AP EAMCET · Maths · Straight Lines

The points (2,3,4),(-1,-2,1) and (5,8,7) are

  1. A collinear
  2. B vertices of a right-angled triangle
  3. C vertices of an equilateral triangle
  4. D vertices of an isosceles triangle
Verified Solution

Answer & Solution

Correct Answer

(A) collinear

Step-by-step Solution

Detailed explanation

Let a lineAC divides at B in ratio m:n A(2,3,4),B-1,-2,1 & C5,8,7 So (-1,2,1)=mx2+nx1m+n,my2+ny1m+n,mz2+nz1m+n ⇒-1,2,1=5m+2nm+n,8m+nm+n,7m+4nm+n ⇒-1=5m+2nm+n,-2=8m+nm+n,1=7m+4nm+n ⇒mn=-12,mn=-12,mn=-12 Ratio are same. It means points are collinear.