Answer(1):
Decay formula is given by

where P= present value = 60
r= percent rate of decay =4.6%=0.046
t= number of years
Plug these values into above formula to get required exponential function.


To find about how many California Tiger Salamanders will be left after 4 years, plug t=4

Hence final answer is approx 50 California Tiger Salamanders .
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Answer(2):




(2x+7)=0 or (x-3)=0
2x=-7 or x=3
x=-3.5 or x=3
Hence final answer is x=-3.5 , x=3.
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Answer(3):



Hence standard form is

where a=-4.9, b=7.5, c=-0.3
Plug that into quadratic formula





t=0.041, t=1.49
Hence final answer is t=0.041, t=1.49