<h3>
Answer:</h3>
60 days
<h3>
Explanation:</h3>
Half-life is the amount of time it takes half of a substance to decay away.
Guess and Check
One method for solving half-life problems like this is to guess and check. To do this, we can continue to divide 475mg by 2 until we get to 30mg.
- 475 ÷ 2 = 237.5
- 237.5 ÷ 2 = 118.75
- 118.75 ÷ 2 = 59.375
- 59.375 ÷ 2 = 29.6875
As seen here, it takes approximately 4 half-lives for this sample of Ra-225 to decay to 30mg. Now, we can multiply 4 by the length of the half-life, 15 days.
Fractions
Another way to solve this is to use fractions.
- 16 is equivalent to
.
This means that it takes 4 half-lives for 475mg to decay to 30mg. Using the same method above, we can tell that 4 half-lives are 60 days.
Important Note
In this question, I rounded occasionally. So, not all of the values are exact, but they are all very close.
Answer:
In the first equation x=4 or x=-3
In the second equation x=-4 or x=3
Explanation:
The first equation x^2 − x − 12 can be factorized as follows:
x^2-4x+3x-12
x(x-4)+3(x-4)
x-4=0 or x+3=0
x=4 or x=-3
It is noteworthy that -x was rewritten as -4x+3x in order to solve the equation
The second equation x^2 + x − 12 can be factorized as below:
x^2+4x-3x-12
x(x+4)-3(x+4)
x+4=0 or x-3=0
x=-4 or x=3
It is noteworthy that +x was rewritten as 4x-3x in order to solve the equation
I was able to find the questions to complete with the verbs saber and conocer:
- ¿<u>Conoces</u> a muchas personas aquí?
- ¿<u>Sabes</u> jugar al tenis?
- ¿<u>Sabes</u> cocinar bien?
- ¿<u>Conoces</u> a los dueños del apartamento?
- ¿<u>Sabes</u> qué tiendas están cerca (close by)?
<u>Saber/conocer</u>
Both verbs (saber and conocer) express the idea of ''knowing". The difference is that you use ''saber'' to talk about facts or learned skills, and you use ''conocer'' when you have familiarity with the thing, person or place you are saying you know.
Check more information in the following link brainly.com/question/22707306?referrer=searchResults
