Question

​Given that the equation ax​³+4x²-5x-10=​​​​​​​​0 and ax³-9x-2=​​​​0 have a common root.What are the possible values of a? ​

Answer 1

Explanation:

Let r be the common root of the given equations.

Then we have:

ar³ + 4r² - 5r - 10 = 0 ...(1)

and

ar³ - 9r - 2 = 0 ... (2)

Subtracting equation (2) from equation (1), we get:

13r² - 3r - 8a = 0

Solving for r using quadratic formula, we get:

r = [3 ± sqrt(9 + 52a)]/26

For r to be a real number, the discriminant of the quadratic expression inside the square root must be non-negative:

9 + 52a ≥ 0

Solving for a, we get:

a ≥ -9/52

Therefore, the possible values of a are all real numbers greater than or equal to -9/52.