Use the quadratic formula to solve the equation. If necessary, round to the nearest hundredth.
x^2-21=-4x

a. 7,3
b. -7,4
c. 7,-3
d. -7,-3

Ared balloon starts at 7.3 meters off the ground and rises at 2.6 meters per second. a blue balloon starts at 12.4 meters off the ground and rises at 1.5 meters per second. when will the balloons be at the same height?

Missouri has a shape that is similar to a trapezoid with bases of about 198 miles and 276 miles and a height of about 270 miles. what is the area of missouri in square miles? explain how you found the answer.

Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)