Question

If one of the root of the quadratic equation x² + kx + 6 = 0 is 3, then the other root of the equation is ?
1. 3
2. -3
3. 2
4. -2

Answer 1

Correct Answer - Option 3 : 2

Concept:

For any quadratic equation ax2 + bx + c = 0, sum of roots is -b/a.

Calculation:

If one of the root of the quadratic equation x2 + kx + 6 = 0 is 3, then it will satisfy the quadratic equation.

⇒ 3² + 3k + 6 = 0  ⇒ 15 + 3k = 0   ⇒ k = - 5

So, now our quadratic equation will be x2 - 5x + 6 = 0

Let other root is α, then sum of roots = -b/a = 5

⇒ α + 3 = 5

⇒  α = 2

Hence, option 3 is correct.