4. Math on the Spot Solve each system by substitution. \( \begin{array}{ll}\text { A. }\left\{\begin{array}{l}y=3 x \\ y=x+4\end{array}\right. & \text { B. }\left\{\begin{array}{l}x-y=4 \\ x+2 y=4\end{array}\right.\end{array} \)

If the graph of the function \( f(x) = 2x + 3 \) is reflected over the line \( y = x \), what is the equation of the resulting inverse function?

What does the exponent in an expression indicate?

sait se un nombre nél telque \( \left|x-\frac{1}{2}\right|<\frac{2}{2} \) onpore \( A=\frac{2 x+5}{x+1} \) et \( B=2 x^{2}-8 x+5 \) 1 - Montur que \( 1<x<4 \) 2 a - Dommer un encidroment de \( A \). \( b \) - renfier que \( A=2+\frac{3}{x+1} \) pus montrenque \( \frac{13}{5} \) C-Dédurs léncadermend liptus préís ele A. 3 -a Donner l'encachernent de \( B \).

Exercice \( 4: \) (Bonus) \( x, y \) et \( z \) sont des nombres réels strictement positifs. 1- Développer : \( \left(\sqrt{x}-\frac{1}{\sqrt{x}}\right)^{2} \) 2- En déduire que : \( x+y+z+\frac{1}{x}+\frac{1}{y}+\frac{1}{z} \geq 6 \)

26 If \( (x-3)+y i=5 \) i, then \( x \times y=\cdots \) \( \begin{array}{lll}\text { (a) } 15 & \text { (b) }-15 & \text { (c) } 8\end{array} \)