NCERT Solutions for Class 12 Maths Chapter 4 Exercise 4.3 Determinants - FREE PDF Download
FAQs on NCERT Solutions for Class 12 Maths Chapter 4 Determinants Ex 4.3
1. What are minors and cofactors in the context of NCERT Solutions for Class 12 Maths Chapter 4 Determinants Exercise 4.3?
Minors are obtained by deleting the row and column of a specific element in a determinant, then taking the determinant of the resulting submatrix. Cofactors are the signed minors, calculated by multiplying each minor by (-1)i+j depending on the position of the element. Mastering these steps is essential for solving Determinants as per CBSE 2025–26 Maths curriculum.
2. How do you calculate the minor of an element in a determinant (Class 12 Maths Chapter 4)?
To calculate the minor of an element aij, remove the element’s row and column from the determinant, then compute the determinant of the remaining submatrix. This process is key in solving Exercise 4.3 NCERT Solutions for Class 12 Mathematics.
3. Why are cofactors important when finding the value of a determinant in Exercise 4.3?
Cofactors are crucial because they allow you to expand a determinant along any row or column, using the formula: sum of each element multiplied by its cofactor. This method is required for many problems in Exercise 4.3 and supports advanced matrix operations in the NCERT Class 12 Maths syllabus.
4. What steps should you follow to solve problems on cofactors and minors for NCERT Solutions Class 12 Maths Chapter 4 Exercise 4.3?
Follow these steps as per the CBSE pattern:
- Identify the element for which you need the minor or cofactor.
- Delete its row and column to form the submatrix.
- Calculate the determinant of this submatrix (gives the minor).
- Apply the sign rule to get the cofactor, using (-1)i+j.
5. How can students avoid common mistakes while solving minors and cofactors questions in Exercise 4.3 Class 12 Maths?
Students should:
- Pay close attention to row and column deletion for each minor.
- Remember to use the correct sign convention when finding cofactors.
- Double-check their submatrix calculations.
- Systematically write each step to prevent errors.
6. How are the concepts of minors and cofactors applied in other chapters or real-life mathematical problems?
Minors and cofactors from Chapter 4 are foundational for more advanced topics like finding the inverse of a matrix, evaluating complex determinants, and solving systems of linear equations in later chapters. Understanding these concepts is also essential for mathematical applications in engineering, physics, and computer science.
7. What is the expansion of a 3×3 determinant using cofactors (as per Class 12 Maths Chapter 4)?
The expansion of a 3×3 determinant along the first row is:
Δ = a11A11 + a12A12 + a13A13, where each Aij is the cofactor for element aij. This process is directly addressed in Exercise 4.3 of the NCERT Solutions.
8. How are signs assigned to cofactors in Class 12 Chapter 4 Determinants?
The sign of each cofactor is determined by its position using the formula (-1)i+j, where i = row number and j = column number. Alternate signs start from positive in the top-left corner of the determinant matrix, following the checkerboard pattern.
9. How does Exercise 4.3 help in mastering determinants for board exams?
Exercise 4.3 focuses on stepwise calculation of minors and cofactors, which are key for all determinant-based problems. Mastery ensures students can confidently expand determinants, solve equations, and apply these skills in higher-level maths questions—directly benefiting their CBSE 2025–26 board performance.
10. What are the prerequisites for understanding NCERT Solutions for Class 12 Maths Chapter 4 Determinants Exercise 4.3?
Students should have a clear understanding of:
- Basic matrix concepts (rows, columns, order of matrix)
- How to compute 2×2 and 3×3 determinants
- Sign conventions in algebra
11. Can the method of finding minors and cofactors be used for determinants larger than 3×3 in Class 12 Maths?
Yes, the same process of finding minors and assigning signs for cofactors applies to determinants of any size. However, with higher order determinants, the expansion uses recursion, breaking down into smaller determinants repeatedly. This concept is also aligned with the NCERT Class 12 curriculum.
12. How should students structure their answers in NCERT Solutions for Class 12 Maths Chapter 4 for maximum marks?
- Write each calculation step clearly, including which row/column is being expanded.
- Show minors and apply the sign rule for cofactors explicitly.
- Include final summaries for determinant values.
- Use proper mathematical notation as per CBSE guidelines.
13. What if two rows or columns are identical in a determinant—how does it impact minors and cofactors?
If two rows or columns in a determinant are identical, the entire determinant evaluates to zero. As a result, the minors and corresponding cofactors calculated for that matrix will either be zero or structured such that their expansion sum is zero, making it a useful shortcut for checking results in Exercise 4.3.
14. How do determinants, minors, and cofactors help in solving systems of linear equations as per the NCERT Solutions?
Determinants and their cofactors are used in Cramer's Rule to solve systems of linear equations. Each variable's value is found by substituting the column of constants into the determinant and dividing by the main determinant. This method relies on correct determination of minors and cofactors for accurate solutions.
15. What is a common misconception about calculating cofactors in Class 12 Determinants, and how can students avoid it?
A common mistake is forgetting to apply the sign convention (-1)i+j when finding each cofactor, especially when working quickly. Students should always check each sign as they calculate minors to avoid incorrect final answers in board-level and competitive exams.

















