(b) Let \( f(x)=x^{3}+a x^{2}+b x-3 \). When \( f(x) \) is divided by \( x-1 \) the remainders are 1 and when divide by \( x+1 \) the remainder is 9 . Find the values of \( a \) and \( b \). (c) (i) Solve the canation \( x^{4}+x^{3}-21 x^{2}-x+20=0 \)

Résoudre dans \( \mathbb{C}: \mathrm{z}^{7}=1 \)

\( 1 \leftarrow \) Show that \( A I=I A=A \). \( A=\left[\begin{array}{rr}1 & 8 \\ -2 & 2\end{array}\right] \)

Calcule todos los valores de a para los cuales la matriz \( A=\left[\begin{array}{lll}a & 0 & 4 \\ 1 & 1 & a \\ a & 1 & 2\end{array}\right] \) es no invertit

Rewrite the following without an exponent \[ (-7)^{-2} \]

Three-fifths of Jesse Black's inventory was destroyed by fire. He sold the remaining part, which was slightly damaged, for two-thirds of its value and received \( \$ 3400 \). (a) What was the value of the destroyed part of the inventory? (b) What was the value of the inventory before the fire? (a) The value is \( \$ \square \). (Round to the nearest cent as needed.)