Urgent: Find value of X

An arrow is shot vertically upward at a rate of 180ft/s. use the projectile formula h=−16t2+v0t to determine at what time(s), in seconds, the arrow is at a height of 420ft. round your answer(s) to the nearest tenth of a second.

Which shows the correct substitution of the values a,b and c from the equation 1=-2x+3x^2+1

What is the simplified form of (3.25x10^3)(7.8x10^6) written in scientific notation?