Question

Find the values of k for which the quadratic equation $(k+4)x^2+(k+1)x+1=0$ has equal roots.

Select all that apply.

• A. 4
• B. 5
• C. -5
• D. -3

Answer 1

Answer: (B), (D)

The correct options are
B

5

D

-3

Let D be the discriminant of the given equation

We have $a=k+4,b=k+1andc=1$

$\therefore D=b^2-4ac$

$\Rightarrow D=(k+1{)}^2-4(k+4)$

$\Rightarrow D=k^2-2k-15=(k-5)(k+3)$

If the roots of the given equation are real, then

$D=0\Rightarrow (k-5)(k+3)=0\Rightarrow k=5,-3$