CBSE Class 12 Mathematics 2026 Main Paper 65(B) · Q212 Marksmatrix_polynomials
CBSE Class 12 Mathematics 2026 Main Paper 65(B) · Question 21 (Matrices)
For A=[[3,1],[2,1]], find a,b such that A²+aA+bI=0. OR Using determinants, find the line through (−1,−1) and (1,3).
Alternative 1 2 Marks
For A=[[3,1],[2,1]], find a,b such that A²+aA+bI=0.
Answer: a=−4, b=1.
- Compute A²=[[11,4],[8,3]].
- The off-diagonal entries force a=−4.
- Either diagonal entry then gives b=1.
Alternative 2 2 Marks
Using determinants, find the line through (−1,−1) and (1,3).
Answer: y=2x+1.
- Set det([[x,y,1],[−1,−1,1],[1,3,1]])=0.
- Expand to get −4x+2y−2=0.
- Simplify to y=2x+1.