Answer:
It will take approximately 3.34 hours for the drug to decay to 90% of the original dosage
Step-by-step explanation:
As suggested, we use the formula for exponential decay:
From the given information, the half life of the drug in blood id 22 hours, so that means that it takes that number of hours to go from the initial value 
, to a final value equal to 
. Using this information we can find the decay rate "k" by solving for this parameter in the formula, and using the natural log function to bring the exponent down:
Now we use this value for the decay rate "k" to calculate how long it would take to decay to 90% of the original dose;
8x + 5 = 3x + 15
8x - 3x = 15 - 5 (put same kinds of number on one side and change the signs)
5x = 10 (simplify)
5x/5 = 10/5 (simplify)
x = 2 (answer)
hope this helps
Answer:
-2x+2y+3z=0
-2x-y+z=-3
2x+3y+3z=5
---------------
-2x+2y+3z=0
-2x-y+z=-3
---------------- Subtract
3y + 2z = 3 Eqn A
=========================
-2x-y+z=-3
2x+3y+3z=5
---------------- Add
2y + 4z = 2
6y + 4z = 6 Eqn A times 2
------------------------------------ Subtract
-4y = -4
y = 1
-----------------
z = 0
-------------------
x = 1
Answer:
(-4, 5)
Step-by-step explanation (work shown in attached picture):
1) Since x is already isolated in the first equation, substitute that value for x into the other equation to find y. So, substitute 16-4y for the x in 3x + 4y = 8, then solve for y. This gives us y = 5.
2) Now, substitute that given value for y back into any one of the equations to find x. I chose to do it in the first equation. Substitute 5 for the y in x = 16-4y, then solve for x this time. This gives us x = -4.
Since x = -4 and y = 5, the solution is (-4, 5).
