Question

The value of $a$ for which the equations $x^{3}+a x+1=0$ and $x^{4}+a x^{2}+1=0$ have a common root is

• A. -2
• B. -1
• C. 1
• D. 2

Answer 1

Answer: (A)

Let $a=-2$,
$\therefore x^{3}-2 x+1=0$ and $x^{4}-2 x^{2}+1=0$
Put $x=1$, we get
$1-2+1=0$ and $1-2+1=0$
$\Rightarrow 0=0$ and $0=0$
Hence, required value is $a=-2$