Question

The equation whose roots are $5$ times the roots of $x^4+1=0$, is :

• A. $x^4+5=0$
• B. $x^4+25=0$
• C. $x^4+125=0$
• D. $x^4+625=0$

Answer 1

The correct option is D $x^4+625=0$

In $x^4+1=0$
Replacing $x\to \frac{x}{5}$, we get
${\left(\frac{x}{5}\right)}^4+1=0\Rightarrow x^4+625=0$