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Question

What is \(\begin{vmatrix} \dfrac{1}{a} & bc & a^3 \\ \dfrac{1}{a}+\dfrac{1}{b} & c(a+b) & a^3+b^3 \\ \dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c} & ab+bc+ca & a^3+b^3+c^3 \end{vmatrix}\) equal to?

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

\(0\)

Applying the row operations \(R_3 \to R_3 - R_2\) and then \(R_2 \to R_2 - R_1\) reduces the rows to \((1/a, bc, a^3)\), \((1/b, ca, b^3)\) and \((1/c, ab, c^3)\). Scaling these rows by \(a, b, c\) respectively makes the second column exactly \(abc\) times the first column, so the two columns become proportional. Hence the determinant equals 0.

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Similar Questions

  1. The value of the determinant \(\left| {\begin{array}{*{20}{c}} {1 - {\rm{\alpha }}}&{{\rm{\alpha }} - {{\rm{\alpha }}^2}}&{{{\rm{\alpha }}^2}}\\ {1 - {\rm{\beta }}}&{{\rm{\beta }} - {{\rm{\beta }}^2}}&{{{\rm{\beta }}^2}}\\ {1 - {\rm{\gamma }}}&{{\rm{\gamma }} - {{\rm{\gamma }}^2}}&{{{\rm{\gamma }}^2}} \end{array}} \right|\) is equal to

  2. The element in the i th row and the j th column of a determinant of third order is equal to 2(i + j). What is the value of the determinant?

  3. Let p, q and r be three distinct positive real numbers. If \(\rm D = \left| {\begin{array}{*{20}{c}} \rm p&\rm q&\rm r\\ \rm q&\rm r&\rm p\\ \rm r&\rm p&\rm q \end{array}} \right|,\)  then which one of the following is correct?

  4. If a 1, a 2, a 3, _ _ _ _ _, a 9are in GP, then what is the value of the following determinant?

    \(\left| {\begin{array}{*{20}{c}} {{ln\:a_1}}&{{ln\:a_2}}&{{ln\:a_3}}\\ {{ln\:a_4}}&{{ln\:a_5}}&{{ln\:a_6}}\\ {{ln\:a_7}}&{{ln\:a_8}}&{{ln\:a_9}} \end{array}} \right|\)

  5. What is the value of the determinant \(\left| {\begin{array}{*{20}{c}} {\rm{i}}&{{{\rm{i}}^2}}&{{{\rm{i}}^3}}\\ {{{\rm{i}}^4}}&{{{\rm{i}}^6}}&{{{\rm{i}}^8}}\\ {{{\rm{i}}^9}}&{{{\rm{i}}^{12}}}&{{{\rm{i}}^{15}}} \end{array}} \right|\)  where \(\rm i = \sqrt {-1}\) ?

  6. If
     then what is f(-1) + f(0) + f(1) equal to?
  7. If a + b + c = 4 and ab + bc + ca = 0, then what is the value of the following determinant?

    \(\left| {\begin{array}{*{20}{c}} {{a}}&{{b}}&{{c}}\\ {{b}}&{{c}}&{{a}}\\ {{c}}&{{a}}&{{b}} \end{array}} \right|\)

  8. Let \(A = \left| {\begin{array}{*{20}{c}} p&q\\ r&s \end{array}} \right|\)

    where p, q, r and s are any four different prime numbers less than 20. What is the maximum value of the determinant?

  9. If \(\left| {\begin{array}{*{20}{c}} x&-3i&1\\ y&1&{i}\\ 0&2i&-i \end{array}} \right|=6+11i\)  , then what are the values of x and y respectively?

  10. If \(\left| {\begin{array}{*{20}{c}} {\rm{x}}&{\rm{y}}&0\\ 0&{\rm{x}}&{\rm{y}}\\ {\rm{y}}&0&{\rm{x}} \end{array}} \right| = 0\) , then which one of the following is correct?


Important Questions from Evaluation of Determinants

  1. The value of the determinant \(\left| {\begin{array}{*{20}{c}} {1 - {\rm{\alpha }}}&{{\rm{\alpha }} - {{\rm{\alpha }}^2}}&{{{\rm{\alpha }}^2}}\\ {1 - {\rm{\beta }}}&{{\rm{\beta }} - {{\rm{\beta }}^2}}&{{{\rm{\beta }}^2}}\\ {1 - {\rm{\gamma }}}&{{\rm{\gamma }} - {{\rm{\gamma }}^2}}&{{{\rm{\gamma }}^2}} \end{array}} \right|\) is equal to

  2. The element in the i th row and the j th column of a determinant of third order is equal to 2(i + j). What is the value of the determinant?

  3. If x, y, z are distinct real numbers and \(\left| {\begin{array}{*{20}{c}} x&{{x^2}}&{2 + {x^3}}\\ y&{{y^2}}&{2 + {y^3}}\\ z&{{z^2}}&{2 + {z^3}} \end{array}} \right| = 0\), then xyz =

  4. If A + B + C = \(\pi \), then, the value of \(\left| {\begin{array}{*{20}{c}} {\sin \left( {A + B + C} \right)}&{\sin B}&{\cos C}\\ { - \sin B}&0&{\tan A}\\ {\cos \left( {A + B} \right)}&{ - \tan A}&0 \end{array}} \right|\) is

  5. Let p, q and r be three distinct positive real numbers. If \(\rm D = \left| {\begin{array}{*{20}{c}} \rm p&\rm q&\rm r\\ \rm q&\rm r&\rm p\\ \rm r&\rm p&\rm q \end{array}} \right|,\)  then which one of the following is correct?

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