1.

If the equation `x^(4)+bx^(3)y+cx^(2)y^(2)+dxy^(3)+ey^(4)=0` represent two pairs of perpendicular lines, thenA. `b+d=1 and e=-1`B. `b+d=0 and e=-1`C. `b+d=0 and e=1`D. none of these

Answer» Correct Answer - B
Let `x^(2)+alpha xy-y^(2)=0 and x^(2)+beta xy-y^(2)=0` be two pairs of perpendicular lines given by the equation
`x^(4)+bx^(3)y+cx^(2)y^(2)+dxy^(3)+ey^(4)=0`. Then,
`x^(4)+bx^(3)y+cx^(2)y^(2)+dxy^(3)+ey^(4)=(x^(2)+alpha xy-y^(2))(x^(2)+beta xy-y^(2))`
On equating the coefficients of like terms, we get
`e=-1, b=beta+alpha, c=alpha beta and d=-beta-alpha`
`rArr" "b+d=-, e=-1`


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