Which of the following second , degree eqation represented a pair of straight lines ?

Options

A. `x^2-xy-y^2=1`
B. `-x^2+xy-y^2=1`
C. `4x^2-4xy+y^2=4`
D. `x^2+y^2=4`

Answer

C

Explanation

We know that , general equation of second degree represent pair of straight line , if `|{:(a,h,g),(h,b,f),(g,f,c):}|=0`
Clearly , option (c) satisfy these requirements as `|{:(4,-2,0),(-2,1,0),(0,0,-4):}|=4(-4-0)+2(8-0)=-16+16=0`