10th/9th (Foundation) Physics, Chemistry, Math Forum

Maths (Rational No.s)

Maths (Rational No.s)

by Shubh Majumdar -
Number of replies: 5

\( \frac{ \sqrt{7-1} }{ \sqrt{7+1} } - \frac{ \sqrt{7+1} }{ \sqrt{7-1} } =a+b \times \sqrt{7} \)

 

Find the value of  "a" & "b". Plz explain the process

In reply to Shubh Majumdar

Re: Maths (Rational No.s)

by Tanvi Mehta -

I think in the question, it is just 7 that should be inside the root.You can simply rationalize the two terms and then take LCM.

a=8/3

b=-2/3

In reply to Tanvi Mehta

Re: Maths (Rational No.s)

by Mehnas Saleem -

Can you please explain step by step because my answer for a is -2/3 but b is zero .

In reply to Mehnas Saleem

Re: Maths (Rational No.s)

by Tanvi Mehta -

I think the given expression should be \(\(\frac {{\sqrt 7-1}}
{{\sqrt 7+1}}-\frac{{\sqrt 7+1}}
{{\sqrt 7-1}} = a+ b\sqrt 7\)
\).Even now if you are unable to do it then you can attach your working here so that others can have a look.

In reply to Tanvi Mehta

Re: Maths (Rational No.s)

by Mehnas Saleem -

I  did know that.My working is as follows

                          (√7 -1)(√7-1)⁄ (√7+1)(√7-1) - (√7+1)(√7+1)/ (√7-1)(√7+1)

                          =(7-2√7+1)/6 - (7+2√7+1)/6

                          =(8-2√7 - 8 -2√7)/6

                          =-4√7/6

                          =-2√7/3

 

 

 

 

 

In reply to Mehnas Saleem

Re: Maths (Rational No.s)

by Tanvi Mehta -

The working looks fine which means the answer for a should be 0 instead of 8/3, b=-2/3.