Question

Which of the following equations has 2 as a root?

विकल्प

• x² – 4x + 5 = 0

• x² + 3x – 12 = 0

• 2x² – 7x + 6 = 0

• 3x² – 6x – 2 = 0

Answer 1

2x² – 7x + 6 = 0

Explanation:

(A) Substituting x = 2 in x² – 4x + 5, we get

(2)² – 4(2) + 5

= 4 – 8 + 5

= 1 ≠ 0

So, x = 2 is not a root of x² – 4x + 5 = 0

(B) Substituting x = 2 in x² + 3x – 12, we get

2)² + 3(2) – 12

= 4 + 6 – 12

= –2 ≠ 0

So, x = 2 is not a root of x² + 3x – 12 = 0

(C) Substituting x = 2 in 2x² – 7x + 6, we get

2(2)² – 7(2) + 6

= 8 – 14 + 6

= 14 – 14

= 0
So, x = 2 is a root of 2x² – 7x + 6 = 0

(D) Substituting x = 2 in 3x² – 6x – 2, we get

3(2)² – 6(2) – 2

= 12 – 12 – 2

= –2 ≠ 0
So, x = 2 is not a root of 3x² – 6x – 2 = 0