Dr/dt= 8cmM-¹
dA/dt = ?
but A= πr²
so dA/dr =2πr
but recall
dA/dt = dA/dr • dr/dt
dA/dt = 2πr • 8cmM-¹
dA/dt = 2×π×39 ×8 = 624cm²M-1
Answer:

Step-by-step explanation:
The above question is in the form of an exponential decay. The equation for an exponential decay is given by:

where y and x are variables, b < 1, a is the initial value of y (that is the value of y when x = 0).
Let y represent the number of trees left and x represent the number of months. Given that there is currently 2.5 billion trees, therefore a = 2.5 * 10⁹, b = 0.5% = 0.005. The equations becomes:

Answer:
gu h-onarach tha mi a ’miannachadh gum b’ urrainn dhomh do chuideachadh, ach tha feum agam air puingean airson mo cheistean fhìn duilich!
Step-by-step explanation: