a rock is thrown upward with a velocity of 18 meters per second from the top of a 38 meter high cliff, and it misses the cliff on the way back down. When will the rick be 12 meters from ground level

h=-9.8t^2+18t+36

want h=4

therefore

-9.8t^2+18t+32=0

t=(-1/19.6)-18+/-sqrt(324+1254.4); sqrt term is equal to 39.73, use negative root only

t=(-1/19.6)(-57.73)=2.95 seconds

option 3 . (5x + 1) - (-10x + 6)

step-by-step explanation:

option 1 :

(4x + 3) + (-9x + 4)

or 4x+3 -9x + 4

or -5x + 7

option 2

(x - 2) - (6x - 9)

or x-2-6x + 9

or -5x + 7

option 3

(5x+ + 6)

or 5x + 1 + 10x -6

or 15x -5

option 4

-4x+2x+7-3x

-7x + 2x + 7

-5x + 7

hence only option 3 did   not satisfy the given simplify expression.