Question

If b${}^2\ge 4ac$ for the equation $a{x}^4+b{x}^2+c=0$, then all the roots of the equation will be real if

• A. b>0, a<0, c>0
• B. b<0, a>0, c>0
• C. b>0, a>0, c>0
• D. b>0, a>0, c<0

Answer 1

Answer: (C)

Given : $a{x}^4+b{x}^2+c+0$
Equation will be real if D $\ge$ 0
$\Rightarrow b^2-4ac\ge 0\Rightarrow b^2\ge 4ac$