The GATE Grind

GATE Matrix Theory: Inner Products and Quadratic Forms – Previous Year Questions

10 GATE previous year questions on Inner Products and Quadratic Forms (Matrix Theory, Statistics) with answers and explanations, from every paper.

  1. GATE 2021 ST Q39 (2 marks, Multiple choice) – Let M be all symmetric positive definite real 3×3 matrices,and S=A∈M:A⁵⁰−A⁴⁸/4=0. How many elements are in S?
  2. GATE 2022 ST Q23 (1 mark, Numerical answer) – A unit vector u∈ℝ⁴ is orthogonal to S=x:x₁+x₂+x₃+x₄=0. Let v=(1,−2,1,1)ᵀ. If u and v−αu are orthogonal,find α² to two decimals.
  3. GATE 2022 ST Q36 (2 marks, Multiple choice) – A symmetric 3×3 matrix M has eigenvalues −1,1,2 and corresponding unit eigenvectors u,v,w. If Mx=u+2(v+w) and M²y=u−(v+2w),find x+y ².
  4. GATE 2022 ST Q47 (2 marks, Multiple select) – M is symmetric 3×3 with eigenvalues 1,2,3. N has real eigenvalues and MN+NᵀM=3I. Which cannot be eigenvalues of N?
  5. GATE 2023 ST Q36 (2 marks, Multiple choice) – For a real n×n matrix A: I:if A is symmetric,there exists c≥0 for which A+cI is symmetric positive definite. II:if A is symmetric positive…
  6. GATE 2023 ST Q59 (2 marks, Numerical answer) – In ℝ³ with standard inner product,the orthonormal basis is v₁=(1,−1,1)ᵀ/√3,v₂=(1,2,1)ᵀ/√6,v₃=(1,0,−1)ᵀ/√2. For u=(a,b,c)ᵀ,its inner products with…
  7. GATE 2024 ST Q15 (1 mark, Multiple choice) – In standard ℝ², u=(a,b)ᵀ has inner products 2 with (1,2)ᵀ and −1 with (4,−2)ᵀ. Which holds?
  8. GATE 2025 ST Q13 (1 mark, Multiple choice) – Let S=(x,y,z)∈ℝ³∖0:z=−(x+y). Define S⊥=v∈ℝ³:v·s=0 for every s∈S. Which holds?
  9. GATE 2026 ST Q26 (1 mark, Numerical answer) – In ℝ⁴ let U=x:x₁+x₂+x₄=0,x₃=0. Find dim U⊥ (integer).
  10. GATE 2026 ST Q51 (2 marks, Multiple select) – A=pmatrix3&1&1\\1&0&2\\1&2&0pmatrix and S=x∈ℝ³:xᵀAx=1. Which hold?