SSC CGL 2022 PYQ — Question 60

SSC CGL - 06 Dec 2022 - Shift 4 • Quantitative Aptitude • Q60

If mxm - nxn = 0, then the value of 1xm+xn{{1} \over x^m+x^n} + 1xm−xn{{1} \over x^m-x^n} in terms of xn is : 

Where x, m, n are > 0.

Show answer & explanation

Correct answer: D

Explanation

The correct answer is option 4 i.e.  2mnxn(n2−m2)\frac{2mn}{x^n(n^2-m^2)}

 mxm - nxn = 0

xm  = nxn/m

then the value of 1xm+xn{{1} \over x^m+x^n} + 1xm−xn{{1} \over x^m-x^n} 

= xm+xn+xm−xn(xm+xn)(xm−xn)\frac{x^m+x^n+x^m-x^n}{(x^m+x^n)(x^m-x^n)}

Put the value of xm 

= (2nxn/m)/[(nxn/m + xn)(nxn/m - xn)]

= (2nxn/m)/[xn(n+mm)(n−mm)(\frac{n+m}{m})(\frac{n-m}{m})]

= 2mn/[xn(n2 - m2)]