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Relation between a, b,c and d are so that ay^2+bxy+cx+dy=0 represents pair of straight lines. A) c=0 ;B) a=0 ; C) ad-bc=0 ; D) ac-bd=0 .The answer should be a) and d) ..Please help.



10-Dec-2015 8:06 AM
~6

Answers (1)


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Let Ax2+2Hxy +By2 +2Gx+2Fy+C=0, be the pair of st. lines.

condition to represent the pair of st. line is: ABC+2FGH -AF2-BG2– AF2=0.

Our equation is ay2+bxy+cx+dy=0

On comparing

A=0, H =b/2, B=a,G=c/2,F=d/2 and C=0.

0+bcd/4 -0-ac2/4 =0

c.(bd-ac)=0

either c=0 or bd-ac=0.



11-12-2015 21:21
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