If the sum of the slopes of the lines given by `x^2-2c x y-7y^2=0` is four times their product, then the value of `c` is_____

Options

A. -2
B. -1
C. 2
D. 1

Answer

C

Explanation

We have , `x^2-2cxy-6y^2=0`
and `m_1+m_2=4m_1.m_2`
From Eq.(i) , we get
`m_1+m_2=(2c)/(-7)`
and `m_1.m_2=(1)/(-7)`
Now , `(m_1+m_1)/(m_1.m_2)=(-7)/((1)/(7))`
`rArr (m_1+m_2)/(m_1.m_2)=2c`
`rArr 4=2c`
`therefore c=2`