Answer:
a)
, b)
, c)
, d) 
Step-by-step explanation:
a) Let assume an initial mass m decaying at a constant rate k throughout time, the differential equation is:

b) The general solution is found after separating variables and integrating each sides:

Where
is the time constant and 
c) The time constant is:


The particular solution of the differential equation is:

d) The amount of radium after 300 years is:

Answer:
The 3rd one as it's cubic
Answer:
We can see that both the triangles are congruent to each other.
So, PQ = TU (CPCT), Thus TU = <u>6</u><u>0</u><u>.</u>