Published by:
CGP EDU Academic Team
Published on: August 13, 2026
The greatest angle of the triangle whose sides are x 2 + x + 1, 2x +1 and x 2 –1
Text Solution
Verified by ExpertsThe correct answer is:
A
Since sides are positive,
∴ x 2 –1 > 0; (x –1) (x + 1) > 0
But when x < –1 then 2x + 1 < 0 so x > 1 only.
Also for x > 1, 
> 
Also a > 
So x 2 + x + 1 is the greatest sides A is greatest angle.
cos A = 
= 
⇒ A = 120 0
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