Answer:
Per hour decay of the isotope is 0.96%.
Step-by-step explanation:
Amount of radioactive element remaining after t hours is represented by

where a = initial amount
t = duration of decay (in hours)
Amount remaining after 1 hour will be,

y = 0.9904a
So amount of decay in one hour = a - 0.9904a
= 0.0096a gms
Percentage decay every hour = 
= 
= 0.958 %
≈ 0.96 %
Therefore, per hour decay of the radioactive isotope is 0.96%.
Choice A is the answer which is the point (1,-1)
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How I got this answer:
Plug each point into the inequality. If you get a true statement after simplifying, then that point is in the solution set and therefore a solution. Otherwise, it's not a solution.
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checking choice A
plug in (x,y) = (1,-1)



This is true because -3 is equal to itself. So this is the answer.
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checking choice B
plug in (x,y) = (2,4)



This is false because 0 is not to the left of -3, nor is 0 equal to -3. We can cross this off the list.
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checking choice C
plug in (x,y) = (-2,3)



This is false because 7 is not to the left of -3, nor is 7 equal to -3. We can cross this off the list.
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checking choice D
plug in (x,y) = (3,4)



This is false because -2 is not to the left of -3, nor is -2 equal to -3. We can cross this off the list.
Let's call your speed "a"
her walking speed is then "2a"
and her friend's scooter speed is 10 a
let's also call the distance you need to walk "d"
so the time (t)you need is:
d/t=a
t=d/a
and her time is:
t=

(half a distance with the speed of 2a and half a distance (d/2) with the distance of 10 a
now we count (we know that her time is 30 minutes)
30=

//multiply by 20a
600a=

600a=6d/divide by 6
100a=d
Now, in order to calculate your time we need to calculate:
t=d/a
but we know how much is d now!
t=

=100
which means that you need 100 minutes, or 1 h 40 minutes!!!
Answer:
Slope = 6
Step-by-step explanation:
Slope = 
The key idea is that, if a vector field is conservative, then it has curl 0. Equivalently, if the curl is not 0, then the field is not conservative. But if we find that the curl is 0, that on its own doesn't mean the field is conservative.
1.

We want to find
such that
. This means



so
is conservative.
2.

Then




so
is conservative.
3.

so
is not conservative.
4.

Then




so
is conservative.