All Exams Test series for 1 year @ ₹349 only
Question

If \(\dfrac{1}{2b+2c}+\dfrac{1}{2c+2a}=\dfrac{1}{a+b}\), then what is \(a^2+b^2+c^2\) equal to?

This question was previously asked in
CDS 2 2026 Maths Question Paper (13-Sep-2026)
The correct answer is

\(3c^2\)

The equation simplifies to \(\dfrac{1}{b+c}+\dfrac{1}{c+a}=\dfrac{2}{a+b}\). Combining the left side: \(\dfrac{a+b+2c}{(b+c)(c+a)}=\dfrac{2}{a+b}\). Cross-multiplying: \((a+b+2c)(a+b)=2(b+c)(c+a)\). Expanding both sides and cancelling the common term \(2c(a+b)\) gives \((a+b)^2=2ab+2c^2\), i.e. \(a^2+b^2=2c^2\). Therefore \(a^2+b^2+c^2=2c^2+c^2=3c^2\).

Was this answer helpful?

Similar Questions

  1. If 2s = a + b + c, then what is s2 + (s - a)(s - b) + (s - b)(s - c) + (s - c)(s - a) equal to ?

  2. What is the square root of 4x 4 + 8x 3 - 4x + 1?

  3. If x + 1/x = 8, then what is x 2 + 1/x 2 equal to?

  4. If a + b = 5 and ab = 6, then what is the value of a 3+ b 3?

  5. If \(x=a+b+\frac{(a-b)^2}{4 a+4 b}\) and \(y=\frac{a+b}{4}+\frac{a b}{a+b}\) then what is the value of (x - a)2 - (y - b)2 ?

  6. If x = \(\frac{\sqrt{3}+1}{\sqrt{3}-1}\) and y = \(\frac{\sqrt{3}-1}{\sqrt{3}+1}\) then what is the value x3 - y3 ? 

  7. The quotient of 8x 3– y 3when divided by 2xy + 4x 2+ y 2is

  8. If 2x - 3y - 7 = 0, then what is the value of 8x 3 - 36x 2y + 54xy 2 - 27y 3 - 340 ?

  9. If \(A + B = \rm \frac{x^2 - 8}{x + 2} \ \ and \ A - B = \frac{-x^2 + 2x + 4}{x + 2}\)  then what is B equal to ?

  10. If \(96 - 64a^3 + \frac{8}{a^6} - \frac{48}{a^3 } - t^3 = 0\)  then what is a 2t + 4a 3 equal to ?


Important Questions from Identities

  1. If \(2x + { {1} \over 3x}= 5, x ≠ 0\) , then what is the value of  \(27x^3+{{1} \over 8x^3}\) ?

  2. If x 2 + 4y 2 = 40, xy = 6 and x > 2y then the value of x - 2y is:

  3. \(\dfrac{(0.73)^3+(0.31)^3}{(0.73)^2-0.73\times0.31+(0.31)^2}\)
  4. \(\dfrac{(5.17-2.19)^2-(5.17+2.19)^2}{11.3223}\)
  5. If a(a + b + c) 2= 1792; b(a + b + c) 2= 1536; c(a + b + c) 2= 768 then what will be the value of a?

Need Expert Advice?
Test Series
CDS img
Defence
UPSC CDS 2026 Mock Test Series
536 Tests 4 Tests Free
1693 Attempts
4.3(174)
English, Hindi
More Questions from CDS

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App