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AP EAMCET · Maths · Straight Lines

If the pair of straight lines 9x2+axy+4y2+6x+by-3=0 represents two parallel lines then

  1. A a=6,b=2
  2. B a=12,b=4
  3. C a=3,b=1
  4. D a=-12,b=1
Verified Solution

Answer & Solution

Correct Answer

(B) a=12,b=4

Step-by-step Solution

Detailed explanation

Given, 9x2+axy+4y2+6x+by-3=0 represents two parallel lines, So, △=0⇒2fgh+abc-af2-bg2-ch2=0 on comparing with ax2+2hxy+by2+2gx+2fy+c=0 We get, △=a×3×b2+9×4×-3-9b22-4×9+3a22=0 ⇒ab2-3b24+a24=48 ...........1 Also for parallel…
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