The function f(t) = -3t^2 + 18t + 21 models the approximate height of an object t seconds after it is launched. How many seconds does it take the object hit the ground ( please help !!! )

Plz answer asap! i will reward brainliest and 12 points for these three questions!take notice: these three questions are completely different! 1) what is the percentage of sugar in the syrup made of 10 kg of water and 4 kg of suugar? 2) what was the original price if after 10% discount it became $450? 3) at first a price was decreased by 12%, then it was disounted again by an additional 5%. what is the percent of the total discount? , and remeber i will award brainliest and 12 points!

One of the solutions to x2 - 2x – 15 = 0 is x = -3. what is the other solution? ox=-5 ox= -1 0 x=1 x = 5

Use long division to indentify (12xto the second power+15x-8)divided by 3x