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JEE Main 2020 · MathsMultiple choiceSingle correctEasyCalculation

JEE Main 8 January 2020, Shift 2, Maths Q54

Question 54 of 75 in this shift, Maths question 4 of 25, Section A.

If

A = \begin{pmatrix} 2 & 2 \\ 9 & 4 \end{pmatrix}

and

I = \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}

, then

10A^{-1}

is equal to :

(1) $6I - A$
(2) $4I - A$
(3) $A - 4I$
(4) $A - 6I$ Official answer

Official answer

Option 4

NTA final key (Jan 2020).

Chapter: Matrices
Topic: Matrix Inverse
Idea tested: Inverse via Characteristic Equation

Same idea in other shifts

Asked 2× in all

8 Apr 2023, Shift 2 · Q4If $A = \begin{bmatrix} 1 & 5 \\ \lambda & 10 \end{bmatrix}$ , $A^{-1} = \alpha A + \beta I$ and $\alpha + \beta = -2$ , then…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.