A ball is thrown from an initial height of 4 feet with an initial upward velocity of \( 31 \mathrm{f} / \mathrm{s} \). The ball's height \( h \) (in feet) after \( t \) seconds is given by the following. \[ h=4+31 t-16 t^{2} \] Find all values of \( t \) for which the ball's height is 18 feet. Round your answer(s) to the nearest hundredth. (If there is more than one answer, use the "or" button.)

Simplify. \[ \frac{9 x^{5} y^{4}}{45 x^{4} y^{2}} \]

1. Realiza las siguientes multiplicaciones. a. \( \frac{2}{3} x \cdot\left(6 x^{2}-5 x+\frac{1}{2}\right) \) b. \( 5 a \cdot\left(3 a^{2}-2 a b+7 b^{2}\right) \) c. \( (4 m-2 n)(3 m+9 n) \) d. \( (8 x-3)\left(x^{2}-5 x+6\right) \)

Factorise fully \( 2 x^{2}+13 x+15 \)

5. Problema de Comida: En una fiesta, hay \( x \) personas. Cada persona trae 3 bocadillos. Si se han traído un total de 27 bocadillos, ¿cuántas personas hay en la fiesta? - Ecuación: \( 3 \mathbf{x}=\mathbf{2 7} \)

Identify the solutions of \( 3+4 \sqrt[3]{x^{2}-13}=-5 \). (1 point) \( \begin{array}{l}2 \sqrt{3},-2 \sqrt{3} \\ \sqrt{13},-\sqrt{13} \\ \sqrt{5},-\sqrt{5} \\ \sqrt{21},-\sqrt{21}\end{array} \)