Question

The value of 'a' for which the point (-a,a) lies inside the circle $x^2+y^2-4x+2y-8=0$ is .

• A. $a\in (-4,1)$
• B. $a\in (1,4)$
• C. $a\in (-1,4)$
• D. $a\in (-4,-1)$

Answer 1

The correct option is A $a\in (-4,1)$

As (-a,a) lies inside the circle,
$\Rightarrow s_1<0\Rightarrow a^2+a^2+4a+2a-8<0\Rightarrow 2a^2+6a-8<0\Rightarrow a^2+3a-4<0\Rightarrow (a+4)(a-1)<0\Rightarrow a\in (-4,1)$