Question 3
Which of the following equations has 2 as a root?
(a) x2−4x+5=0
(b) x2+3x−12=0
(c) 2x2−7x+6=0
(d) 3x2−6x−2=0
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 = 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