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Question
Which of the following equations has 2 as a root?
Options
x2 – 4x + 5 = 0
x2 + 3x – 12 = 0
2x2 – 7x + 6 = 0
3x2 – 6x – 2 = 0
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Solution
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
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