Saturday

January 31, 2015

January 31, 2015

Posted by **Emily** on Thursday, June 20, 2013 at 3:16pm.

I have no idea how to solve this, steps and explanations would be amazing.

- Math Gr 11 -
**Steve**, Thursday, June 20, 2013 at 3:51pmwell, since f(t) is the height of the rock at time t, just set it to 80 and solve for t:

-5t^2 - 5t + 180 = 80

5t^2 + 5t - 100 = 0

t^2 + t - 20 = 0

(t+5)(t-4) = 20

t=4

check:

f(4) = -5(16)-5(4)+180 = 80

**Answer this Question**

**Related Questions**

Math - A person standing near the edge of a cliff 120 feet above a lake throws a...

Math - For this problem, a person standing on the edge of a cliff throws a rock ...

physics - A rock is thrown vertically upward from the edge of a cliff. The rock ...

physics - A rock is thrown vertically upward from the edge of a cliff. The rock ...

physics - A 17-kg rock is on the edge of a 103-m cliff. (a) What potential ...

physics - A rock is thrown upwards from the top of a 100m cliff, on the way down...

physics - A 17-kg rock is on the edge of a 103-m cliff. (a) What potential ...

Physics - A boy kicks a rock off a cliff with a speed of 19.4 m/s at an angle of...

physics - c) A 0.26-kg rock is thrown vertically upward from the top of a cliff ...

pre calc - A rock is dropped form the top of a cliff. It takes 12 seconds to hit...