RD Sharma Class 12 Exercise 5.5 Determinant Solutions Maths - Download PDF Free Online

RD Sharma Class 12 Exercise 5.5 Determinant Solutions Maths - Download PDF Free Online

Updated on 25 Jan 2022, 07:11 PM IST

The CBSE board students use the RD Sharma Solutions to prepare for their public examinations. Therefore, it is recommended to use these books to understand the concepts better in a particular subject. Significantly, the students who find mathematics challenging to solve the sums in the Determinants chapter use the RD Sharma Class 12th exercise 5.5 book. Although not every student gets the opportunity to go for daily mathematics tuition, these books are a boon. Moreover, in RD Sharma solution books, the students can clear their doubts and verify their answers.

RD Sharma Class 12 Solutions Chapter 5 Determinants - Other Exercise

Determinants Excercise: 5.5

Determinant exercise 5.5 question 1

$x = k, y = k, z = k, where \: k \in R$
Hint: The homogeneous system of linear equations has non-trivial solutions when the determinant is zero.
Given:$x + y - 2z =0$

$2x + y - 3z = 0$

$5x + 4y - 9z = 0$
Solution:
The above linear equations can be represented in matrix form i.e.
$A = \begin{bmatrix} 1& 1& -2\\ 2& 1& -3\\ 5& 4& -9 \end{bmatrix}$, $X= \begin{bmatrix} x\\ y\\ z\end{bmatrix}$,$B= \begin{bmatrix} 0\\ 0\\ 0\end{bmatrix}$
Now, $A = \begin{vmatrix} 1 & 1&-2 \\ 2& 1& -3\\ 5& 4& -9 \end{vmatrix}$
$= 1(-9 + 12) -1(-18 + 15) - 2(8 -5)$
$=3 + 3 - 6$
$=0$
So, the given system has non-trivial solutions.
Consider first two equations and put z=k.
$x+ y - 2z =0$
$2x + y -3z = 0$
Solving these equations by Crammer’s rule:
$x = \frac{D_{1}}{D}=\frac{\begin{vmatrix} 2k&1 \\ 3k& 1 \end{vmatrix}}{\begin{vmatrix} 1 & 1\\ 2& 1 \end{vmatrix}} = \frac{-k}{-1}=k$

$y = \frac{D_{2}}{D}=\frac{\begin{vmatrix} 1&2k \\ 2& 3k \end{vmatrix}}{\begin{vmatrix} 1 & 1\\ 2& 1 \end{vmatrix}} = \frac{-k}{-1}=k$
Thus, $x = k, y = k, z = k$ satisfy the third equation.
Hence,$x = k, y = k, z = k$ where $k \in R$

determinants exercise 5.5 question 3

Answer: $x = -7k, y = 8k, z = 13k$, where $k \in R$
Hint: : If $\left | A \right |= 0$, then the system has an infinite number of solutions.
Given:
$3x+y+z=0$
$x - 4y + 3z = 0$
$2 x + 5y - 2z = 0$
Solution:
The above linear equations can be represented in matrix form i.e.
$A = \begin{bmatrix} 3 & 1 & 1\\ 1& -4 & 3\\ 2& 5& -2 \end{bmatrix}, X = \begin{bmatrix} x\\ y\\ z\end{bmatrix}, B = \begin{bmatrix} 0\\ 0\\ 0\end{bmatrix}$
Now,
$\left | A \right | = \begin{vmatrix} 3 & 1& 1\\ 1 & -4 &3 \\ 2& 5& -2 \end{vmatrix}$
$= 3(8 -15) -1(-2 -6) + 1(5+8)$
$= 3(-7) + 8 +15$
$= - 21 + 21$
$= 0$
So, the system of equations has non – trivial solutions.
Consider, first two equation and put z = k
$3 x + y = -k$
$x - 4y = -3k$
Now, By Crammer’s rule:
$x = \frac{D_{1}}{D} = \frac{\begin{vmatrix} -k & 1\\ -3k & -4 \end{vmatrix}}{\begin{vmatrix} 3&1 \\ 1& -4 \end{vmatrix}} = \frac{7k}{-13} = \frac{-7k}{13}$
$y = \frac{D_{2}}{D} = \frac{\begin{vmatrix} 3 & -k\\ 1 & -3k \end{vmatrix}}{\begin{vmatrix} 3&1 \\ 1& -4 \end{vmatrix}} = \frac{-8k}{-13} = \frac{8k}{13}$
$x=\frac{-7k}{13}, y = \frac{8k}{13}$ and $z=k$
or $x = -7k$, $y = 8k$ and $z = 13k$, where $k \in R$
It will satisfy the third equation.
Hence, $x = -7k$, $y = 8k$ and $z = 13k$, where $k \in R$


Determinants exercise 5.5 question 4

Answer: $\lambda = 2, x = k, y =k/2, z = -k,$ where $k \in R$
Hint: The system has non-trivial solution implies that the determinant is zero.
Given: $2\lambda x - 2y + 3z =0$
$x x + \lambda y + 2z = 0$
$2 x + \lambda z = 0 \lambda$
Solution:
Firstly, form 3x3 matrix from the given equations:
Let A = [$2 \lambda$, 2, 3 ]
x $\lambda$ 2
[ 2 0 $\lambda$ ]
We know that, $|A| = 0$
Expanding through first row,
$2\lambda (\lambda ^2 - 0) + 2 (\lambda - 4) + 3 (0 - 2 \lambda ) = 0$
$2\lambda ^3 + 2\lambda - 8 - 6\lambda = 0$
$2\lambda ^3 - 4\lambda - 8 = 0$
$\lambda ^3 - 2\lambda - 4= 0$
Put $\lambda = 2:$
$= (2)^{3} - 2 (2) - 4$
$= 8 - 4 - 4$
$= 0$
As it satisfies the given equation, $\therefore \lambda = 2.$
So, the given linear equation transforms into:
$4x-2y+3z=0$
$x+2y+2z=0$
$2 x+2z=0$
Now, the above equations can be represented in matrix form i.e.
$A = \begin{bmatrix} 4 & -2 & 3\\ 1& 2& 2\\ 2& 0& 2\end{bmatrix}, X = \begin{bmatrix} x\\ y\\ z\end{bmatrix}, B =\begin{bmatrix} 0\\ 0\\ 0\end{bmatrix}$
or $AX=B$
Now, Put z = k from first two equations, we get:
$4 x - 2y = -3k$
$x + 2y = -2k$
Now, By Crammer’s rule:
$x = \frac{D_{1}}{D} = \frac{\begin{vmatrix} -3k &-2 \\ -2k& 2\end{vmatrix}}{\begin{vmatrix} 4 & -2\\ 1 & 2\end{vmatrix}} =\frac{10k}{10} = k$
$y = \frac{D_{2}}{D} = \frac{\begin{vmatrix} 4-3k & 1-2k \end{vmatrix}}{\begin{vmatrix} 4-2 & 12 \end{vmatrix}}=\frac{-5k}{10} = \frac{-k}{2}$

It also satisfies the third equation.
Hence,$x = k$ ,$y = \frac{-k}{2}$ and $z = -k$where $k \in R$

Determinant exercise 5.5 question 5

Answer: $ab+bc+ca=abc$
Hint: The system has non-trivial solution implies that the determinant is zero.
Given: $(a-1) x = y + z$
$(b - 1) y = z + x$
$(c - 1) z = x + y$
Solution:
Take x, y and z to the LHS:
$(a - 1)x - y - z = 0$
$x - (b - 1) y + z = 0$
$x + y - (c - 1) z = 0$
Let $A = [a-1 -1 -1 -1 b-1 -1 -1 -1 c-1 ]$
We know that, $|A|=0$
$=>(a-1)[(b-1)(c-1)-1]+1[-(c-1)-1]-1[1+b-1] = 0$
$=>(a-1)[bc-c-b+1-1]+1[-c+1-1]-1[b] = 0$
$=>(a-1)[bc-c-b]-c-b = 0$
$=>abc-ac-ab-bc+c+b-c-b=0$
$=>abc-ac-ab-bc+c+b-c-b$
$=>ab+bc+ca=abc$
Hence proved.

The Class 12, Mathematics chapter 5, Determinants, consists of five exercises in total. RD Sharma class 12th exercise 5.5, includes the left-out topics from the previous exercises in the same chapter. Concepts like Homogeneous linear equations and non-trivial solutions are present in this exercise. It contains around five questions, including the subparts. If they find it difficult or need a good solutions guide to verify the answers, the RD Sharma Class 12 Chapter 5 Exercise 5.5 is the best option.

A committee of experts provides all the answers given in this book. There are many methods by which a sum is solved. This is to allow the students to select the way that they find easy and go ahead with it. The pattern of the book follows the NCERT syllabus making an opportunity for the CBSE students to follow it. Using the Class 12 RD Sharma Chapter 5 Exercise 5.5 Solution guide to doing their homework will make the students fluent regarding the concept. Students who aim to score high marks in the tests and exams must stick to the RD Sharma Class 12th exercise 5.5 solutions.

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Download the RD Sharma Class 12 Solutions Determinants Ex 5.5 to fully understand the fifth chapter in mathematics. With constant practice, you will find yourself crossing your benchmark score.

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