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Most Important Selected Qs for JEE AdvancedMathematicsStraight Lines

Two equal sides of an isosceles triangle are given by the equations 7 x-y+3=0 and x+y-3=0 and its third side passes through the point (1,-10) . The equation of the third side can be

Options

  1. Ax+3 y+29=0
  2. Bx-3 y=31
  3. C3 x-y=13
  4. D3 x+y+7=0

Correct answer

D. 3 x+y+7=0

Step-by-step solution

m_ A B =7 and m_ A C =-1 Let slope of B C (third side) be m . Now | 7- m 1+7 ~m |= | -1- m 1- m | ( 7- m 1+7 ~m )= ( -1- m 1- m ) Taking '+' sign, we get m ^2+1=0 (no real values of m possible) And taking '-' sign, we get 3 m^2+8 m-3=0 (3 m-1)(m+3)=0 m= 1 3 ,-3 Required equation of third side can be x-3 y-31=0 or 3 x=y+7=0

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