Answer:
18 minutes
Step-by-step explanation:
A = A₀ (½)^(t / T)
where A is the final amount,
A₀ is the initial amount,
t is the time,
and T is the half life.
A = 140 when t = 10. Solve for the half life:
140 = 700 (½)^(10 / T)
0.2 = ½^(10 / T)
log 0.2 = (10 / T) log 0.5
10 / T = 2.32
T = 4.31
When A = 40, t is:
40 = 700 (½)^(t / 4.31)
0.057 = ½^(t / 4.31)
log 0.057 = (t / 4.31) log 0.5
t / 4.31 = 4.13
t = 17.8
Rounded to the nearest whole number, it takes 18 minutes.
Add like terms just like you would anywhere else...
Step-by-step explanation:
g(t) = (t + 1)² − 20.25
0 = (t + 1)² − 20.25
20.25 = (t + 1)²
±4.5 = t + 1
t = -1 ± 4.5
t = -5.5 or 3.5
The zeros are (-5.5, 0) and (3.5, 0).
