Answer:
x = 5
Step-by-step explanation:
The area (A) o a rectangle is calculated as
A = lb ( l is length and b the breadth ), thus
x² + x - 12 × 
= 126 ← factor the quadratic
(x + 4)(x - 3) × = 126 ← cancel the common factor (x - 3)
(x + 4)(x + 9) = 126 ← expand factors using FOIL
x² + 13x + 36 = 126 ( subtract 126 from both sides )
x² + 13x - 90 = 0 ← in standard form
(x + 18)(x - 5) = 0 ← in factored form
Equate each factor to zero and solve for x
x + 18 = 0 ⇒ x = - 18
x - 5 = 0 ⇒ x = 5
However x > 0 ⇒ x = 5
68,642 rounded to the nearest thousand is 69,000.
It's because 68,642 is closer to 69,000 than to 68,000.
I hope it will help you and give a clue for rounding numbers in the future ;)
Answer:
1/2
Step-by-step explanation:
Answer:
Where 
represent the half life and the intial amount would be 
And we want to find the time in order to have a 95% of decay so we can set up the following equation:
If we apply natural log on both sides we got:
And solving for t we got:
So then would takes about 14.26 hours in order to have 95% of the lead to decay
Step-by-step explanation:
For this case we can define the variable of interest amount of Pb209 and for the half life would be given:
Where represent the half life and the intial amount would be
And we want to find the time in order to have a 95% of decay so we can set up the following equation:
If we apply natural log on both sides we got:
And solving for t we got:
So then would takes about 14.26 hours in order to have 95% of the lead to decay
