1.

For real numbers x and y, if `x^2+xy-y^2+2x -y+1=0`, then (a) y can not be between 0 and `8/5` (b) y can not be between `-8/5 and 8/5` (c) y cannnot be between `-8/5 and 0`(d) y cannot be between `-16/5 and 0`

Answer» `x^2+x(y+2)-y^2-y+1=0`
`D>=0`
`(y+2)^2-4(-y^2-y+1)>=0`
`y^2+4+4y+4y^2+4y-4>=0`
`5y^2+8y>=0`
`y(5y+8)>=0`
`(-8/5,0)`
Option C is correct.


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