Question

If the equations $x^2+ax+1=0$ and $x^2-x-a=0$ have a real common root b, then the value of b is equal to

• A. 0
• B. 1
• C. -1
• D. 2
• E. 3

Answer 1

Answer: (C)

Given equations,
$x^2+ax+1=0$
$x^2-x-a=0$
$\because b$ is common root, so $b$ satisfied both equations.
$b^2+ab+1=b^2-b-a$
$=ab+b=-a-1$
$\Rightarrow b(a+1)=-(a+1)$
$\Rightarrow b=-1$