Questions
The product of the perpendicular from (-1,2) to the pair of lines is 2 then the value of k is
a
-43
b
43
c
34
d
-34
detailed solution
Correct option is B
The product of the perpendiculars drawn from the point Px1,y1to the pair of lines represented by the equation ax2+2hxy+by2=0 is ax12+2hx1y1+by12a−b2+4h2Given that the product of the perpendiculars from the point −1,2 to the pair of lines 2x2+kxy+y2=0 is 22=2−12+k−12+222−12+k22=6−2kk2+1Squaring on both sides and then simplify k2+1=3−k29−6k=1k=86Therefore, the value of k is 43Talk to our academic expert!
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The product of the perpendicular from (1,1) to the pair of lines is 1 then
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