SSC CHSL 10 Jan 2017 Shift 2 Paper

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Question : 78 of 100

Marks: +1, -0

Which of the following equations has 3 as a root?

$x^2 − 7x + 12 = 0$
$x^2 − 5x + 12 = 0$
$x^2 + 3x + 12 = 0$
$x^2 + 3x − 12 = 0$

Solution:

(A) :

x^2 − 7x + 12 = 0

⇒

x^2 − 4x − 3x + 12 = 0

⇒

x(x − 4) − 3(x − 4) = 0

⇒

(x − 4)(x − 3) = 0

⇒

x = 3, 4

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