A rock is thrown straight up into the air from a height of 4 feet. The height of the rock above the grond in feet, seconds after it is thrown is given by . For how many seconds will the height of the rock be at least 28 feet above the ground?

5

Step-by-step explanation:

geometry: triangles

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call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

25.45584

c

-by-step explanation:

it would be c