If x=\sqrt{\frac{\sqrt10+1}{\sqrt10-1}} then find 9x^2 - 6x - 6 = ?

SSC CGL Model Paper 7

Question : 63 of 100

Marks: +1, -0

x=√{{√10+1}/{√10-1}}

then find

9x^2 - 6x - 6 = ?

Solution:

x=√{{√10+1}/{√10-1}}

=√ {{√10+1}/{√10-1}×{{√10+1}/{√10+1}}}

={√10+1}/3

= 3x = √10 + 1

⇒ 3x - 1 = √10

Squaring both sides, we get

9x^2 + 1 - 6x = 10

9x^2 - 6x = 9

9x^2 - 6x - 6 = 3

Go to Question:

Prev Question

Next Question