Someone pleas help me ! A sample of a radioactive isotope had an initial mass of 490 mg in the year 1995 and
decays exponentially over time. A measurement in the year 1998 found that the
sample's mass had decayed to 240 mg, What would be the expected mass of the
sample in the year 2005, to the nearest whole number?

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

pi x^2

step-by-step explanation:

pi times x squared