You have to use PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction) to solve this,
Because you don't have any parenthesis or exponents you start with Multiplication/Division. This means you do 4*3 to get 26+5-12
Then, you move to Addition/Subtraction in which you complete left to right, So you do 26+5 to get 31-12
Finally you subtract 31-12 to get 19
N=NOe^-kt
N=mass at time t
NO = initial mass
k= 0.1476
t= time, in days
We are asked to find the half-life, which means you want to find how long it will take for half of the substance to decay/disappear (depending on situation).
If we are looking for half-life, we can simply set N to half of NO (which we are given a value of 40grams for)
Therefore:
N = 20
NO = 40
plugging these values and the value given for k back into the equation you get:
20 = 40e^-0.1476(t)
We are looking for t, so we have to manipulate the formula to get t by itself on one side of the equation.
We can start by dividing 40 from both sides, and you get:
0.5 = e^-0.1476(t)
We have the exponential function "e".
To get rid of e, we can use natural log (ln)
if e^y=x then ln (x) = y
look back at our equation we can set
0.5 = x
-0.1476(t) = y
Rewriting it in natural log form:
ln (0.5) = -0.1476(t)
Plug in ln (0.5) on a calculator to find its value and we get:
-0.693147 = -0.1476(t)
*Note: normally, getting a negative value would suggest that we did something wrong, because you cannot have a negative value as your t (you cannot have negative days), but because there is a negative on both sides of the equation, they will cancel out in this case.
The last step is to simply divide both sides by -0.1476
therefore:
T = 4.696119
But it asks you for the answer to the nearest tenth (one place after decimal pt) so
T (half life) = 4.7 days
Hope that helps :)
Answer:
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Answer:
429
Step-by-step explanation:
y=3+6×(n-1)
n=72
y=3+6×(72-1) = 429
Answer:
(- 2, 2 )
Step-by-step explanation:
Given the 2 equations
y = x + 4 → (1)
y = - 2x - 2 → (2)
Substitute y = x + 4 into (2)
x + 4 = - 2x - 2 ( add 2x to both sides )
3x + 4 = - 2 ( subtract 4 from both sides )
3x = - 6 ( divide both sides by 3 )
x = - 2
Substitute x = - 2 into either of the 2 equations abd evaluate for y
Substituting into (1)
y = - 2 + 4 = 2
solution is (- 2, 2 )
