Alain throws a stone off a bridge into a river below.
The stone's height (in meters above the water), x seconds after Alain threw it, is modeled by:
h(x) = -5x^2+ 10x + 15
How many seconds after being thrown will the stone hit the water?

Acomputer store buys a computer system at a cost of $370.80. the selling price was first at $ 618, but then the store advertised a 20 % markdown on the system. answer parts a and b. a. find the current sale price.

Zed is making a centerpiece for his dining room table by putting sand in a cube-shaped vase. the vase is 0.25 meters in length, width, and height. he bought 25 kg of sand. assume the density of dry sand is 1,602 kgm3. what is the volume of the sand that zed purchased? the volume of the sand is approximately m3. enter your answer as the number that correctly fills in the blank in the previous sentence. if necessary, round your answer to six decimal places, like so: 42.536475

Ireally don't understand this, i'm really an idiot but i want to know how to figure this out. !