Question

If -4 is a root of x2 + px - 4 = 0 and equation 2x2 + px + k = 0 has equal roots, find the value of k. Solve with explaination.

Answer 1

Since -4 is the root of the equation it satisfies the given equation

Therefore we can find the value of p by substituting x=4 in the equation

substituting the value of x=4

16+4p-4=0

4p=12

p=3.

substituting the value of p=3 in the equation

and it also had equal roots therefore

b^2 -4×a×c=0.

p^2-4×k=0.

4×k=9.

k=9÷4.