Mrs Brown gave \( \frac{4}{7} \) of her money to her son. He spent \( \frac{2}{5} \) of the money on a pair of shoes and the rest on two books that cost \( \$ 18 \) each. How much did Mrs Brown have at first?

3. (Unisc-SC) A parte real do número complexo \( z=\frac{1+(3 i)^{2}}{1-i} \) é \( \begin{array}{ll}\text { i) } 1 & \text { d) }-2 \\ \text { b) }-1 & \text { e) }-4\end{array} \)

b) If \( f: f(x)=k x^{2}+(3 k+2) x+6 \) and the \( x \)-coordinate of the vertex of the carve is -2 find \( (1) \) The value of \( k \)

5.(20 poir

b. Soit \( f^{\prime \prime} \) la dérivée seconde de \( f \) sur \( [0 ; 10] \). Montrer que \[ f^{\prime \prime}(x)=\frac{e^{45-x}\left(e^{4,5-x}-e^{-0,6}\right)}{\left(e^{-0.5}+e^{4,5-x}\right)^{3}} \]

\( y=x^{2}+3 x-10 \) and the \( x \)-axis.