91Ó°ÊÓ

Solve. Fireworks Displays. Fireworks are typically launched from a mortar with an upward velocity (initial speed) of about \(64 \mathrm{ft} / \mathrm{sec} .\) The height \(h(t)\) in feet, of a "weeping willow" display, \(t\) seconds after having been launched from an 80 -ft high rooftop, is given by $$h(t)=-16 t^{2}+64 t+80 $$ How long will it take the cardboard shell from the fireworks to reach the ground? (image cannot copy) (graph cannot copy)

Write two expressions, one with parentheses and one without, for the opposite of each polynomial. $$ -12 y^{5}+4 a y^{4}-7 b y^{2} $$

Multiply. Assume that variables in exponents represent natural numbers. $$\left(x^{a}+y^{b}\right)\left(x^{a}-y^{b}\right)\left(x^{2 a}+y^{2 b}\right)$$

Find an equation in slope-intercept form of the line through \((0,7)\) that is parallel to the line \(y=5 x-6\)

Perform the indicated operations. $$ \left(8 r^{2}-6 r\right)-(2 r-6)+\left(5 r^{2}-7\right) $$