Question

matrix multiplication

Answer 1

\[\left[\begin{matrix}a & 2 \\ 2& -1\end{matrix}\right]^{2}\]

Answer 2

\[\left[\begin{matrix}a & 2 \\ 2 & -1\end{matrix}\right]*\left[\begin{matrix}a & 2 \\ 2 & -1\end{matrix}\right]\]
\[\left[\begin{matrix}a^2 +4 & 2a-2 \\ 2a-2 & 4+1\end{matrix}\right]\]
\[\left[\begin{matrix}a^2+4 & 2a-2 \\ 2a-2 & ?\end{matrix}\right]\]

Should be right

Answer 3

that question mark should be a 5

Answer 4

if \[M ^{2}=\left[\begin{matrix}5 & -4\\ -4 & 5\end{matrix}\right]\]
find the value of \[a\]

Answer 5

where's a?

Answer 6

from the previous.

Answer 7

ah

Answer 8

a = -1

you make 2a-2 = -4 and solve

Answer 9

oh, so i would just solve for an equation.
i thought i had to set them equal to each other.
Thanks

Answer 10

well yeah that's what you're doing, you can make the part of M^2 (a^2 +4) = 5, the second part (2a-2)=-4. You can do this for every row/column

Answer 11

ohh. that makes sense
thank you