(Unisinos-RS) Dado o sistema de equa- côes: \[ \left\{\begin{array}{l}4^{x}+3^{y}=43 \\ 4^{x}-3^{y}=-11\end{array}\right. \] o valor de \( x+y \) é: \( \begin{array}{lll}\text { a) } 3 & \text { c) } 5 & \text { e) } 7 \\ \text { b) } 4 & \text { d) } 6 & \end{array} \)

(c) \( 3 x^{2}-x=x^{2}-5 x+6 \)

Rationalize the Denominator: \( \frac{4+\sqrt{7}}{3+\sqrt{7}} \)

Solve the system by graphing each equation and finding the point of intersection. \( \begin{array}{l}y=\frac{-12}{x+4}+3 \\ y-14=(x+6)^{2} \\ x= \\ y=\end{array} \)

(c) \( 3 x^{2}-x=x^{2}-5 x+6 \)

Students stuff envelopes for extra money. Their initial cost to obtain the information for the job was \( \$ 420 \). Each envelope costs \( \$ 0.03 \) and they get paid \( \$ 0.06 \) per envelope stuffed. Let \( x \) represent the number of envelopes stuffed. (a) Express the cost \( C \) as a function of \( x \). (b) Express the revenue \( R \) as a function of \( x \). (c) Determine analytically the value of \( x \) for which revenue equals cost. (a) \( C(x)=\square \) (C in dollars) (b) \( R(x)=\square \) ( \( R \) in dollars) (c) Revenue equals cost when \( x=\square \)