In an animal hospital, 15 units of a certain medicine were injected into a dog. After 45 minutes, only 9 units remained in the dog. Let f(t) be the amount of the medicine present after t minutes. At any time, the rate of change of f(t) is proportional to the value of f(t). Find the formula for f(t).

option 1 is correct.

step-by-step explanation:

y varies inversely with x and constant of variation is 4

the equation will be:

y = k/x

where k =4 so,

y = 4/x

if we put values of x of option 1 in the above equation and find values of y

y = 4/-2 => y =-2

y = 4/-1 => y = -4

y = 4/1 => y = 4

y = 4/2 => y =2

so, all the values of x and y are correct.

if we put values of x given in other options and find value of y we cannot find whole table satisfying the equation.

hence option 1 is correct.

step-by-step explanation:

left be aligning the decimal points is required to not required see the number of digits to the right