Question

SOCORROOOOOOOOOO pfvrr

Answer 1

20º

a)

$\left[\begin{array}{ccc}2&4\\1&2\\0&-1\end{array}\right] .\left[\begin{array}{ccc}1&0\\-3&1\\\end{array}\right] =\left[\begin{array}{ccc}2+(-12)&4\\1+(-6)&2\\3&-1\end{array}\right] =\left[\begin{array}{ccc}-10&4\\-5&2\\3&-1\end{array}\right]$

b)

∄

c)

$\left[\begin{array}{ccc}2&4\\1&2\\0&-1\end{array}\right] .\left[\begin{array}{ccc}2\\-1\\\end{array}\right] = \left[\begin{array}{ccc}4+(-4)\\2(-2)\\1\end{array}\right] = \left[\begin{array}{ccc}0\\0\\1\end{array}\right]$

d)

$\left[\begin{array}{ccc}-10&4\\-5&2\\3&-1\end{array}\right] .\left[\begin{array}{ccc}2\\-1\\\end{array}\right] = \left[\begin{array}{ccc}-20 - 4\\-10 -2\\6 +1\end{array}\right] =\left[\begin{array}{ccc}-24\\-12\\7\end{array}\right]$

e)

Pela propriedade associativa das matrizes o resultado de d) é o mesmo de e), portanto:

 $A(B.C)=\left[\begin{array}{ccc}-24\\-12\\7\end{array}\right]$

21º

$\left[\begin{array}{ccc}-3&y\\x&2\\\end{array}\right] .\left[\begin{array}{ccc}2\\-3\\\end{array}\right] =\left[\begin{array}{ccc}1\\-5\\\end{array}\right] \\\left[\begin{array}{ccc}-6 -3y\\2x - 6\\\end{array}\right] =\left[\begin{array}{ccc}1\\-5\\\end{array}\right]\\\\-6-3y = 1\\-3y = 7\\y =-7/3\\\\2x - 6 = -5\\2x = 1\\x = 1/2$

23ª

Se uma matriz X multiplicada por A₂ₓ₂ resulta em A₂ₓ₂ isso significa que a matriz X é uma matriz identidade de mesma ordem que A.

$X = \left[\begin{array}{ccc}1&0\\0&1\\\end{array}\right]$