Question

If one of the roots of the equation x² + kx - 12 is 4, what is the value of k?

a. -1
b. 0
c. 1
d. 3

Answer 1

To find the value of k, we can use the fact that one of the roots of the equation is 4. By substituting the known value and solving for k using the quadratic formula, we get k = ±4. option c is correct .

Step-by-step explanation:

To find the value of k, we can use the fact that one of the roots of the equation is 4. A quadratic equation of the form ax²+bx+c = 0 can be solved using the quadratic formula. Plugging in the known values, we have:

[(-k ± √(k² - 4(-12)))/2]

Since one of the roots is 4, we can substitute that value into the formula:

[(-k ± √(k² - 4(-12)))/2] = 4

Simplifying and solving for k, we get:

-k ± √(k² + 48) = 8

Squaring both sides:

k² + 48 = 64

Simplifying further:

k² = 16

Taking the square root of both sides:

k = ±4

Therefore, the value of k can be either 4 or -4.