matrix A satisfies A^2 - 3A + I = O. Which expression equals A^-1?

Determinants, Adjoint & Inverse · Question 66 of 87

Question 66

HardOriginal question

$A = \begin{bmatrix}2 & 1 \\ 1 & 1\end{bmatrix}$ satisfies $A^2 - 3A + I = O$ . Which expression equals $A^{-1}$ ?

A - 3I

Correct answerYour answer

3I - A

Correct answerYour answer

3A - I

Correct answerYour answer

3I + A

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Worth noting

$A - 3I$ has the sign the wrong way round: it is $-A^{-1}$ .

Ten questions from Determinants, Adjoint & Inverse, at your own pace.

Ten questions from Determinants, Adjoint & Inverse, at your own pace.