Question

write the value of k for which the quadratic equation x2-4x-k=0 has equal roots​

Answer 1

Answer:

4

Step-by-step explanation:

For a quadratic equation ax

2

+bx+c=0 to have equal roots, D=b

2

−4ac=0

∴D=b

2

−4ac=(−4)

2

−4(1)(k)=0

∴k=4

Answer 2

This is 2nd method to find such type of questions.

For the equal root of the quadratic equation. X = -b/2a .

=> X = -(-4)/(2×1)

=> X = 2.

=> (2)² - 4(2) - k = 0

=> 4 -8-k =0

=> -12-k =0

=> k = -12