The population of a town doubled every 5 years from 1960 to 1975. What is the percentage increase in population in this period ?

800%

Step-by-step explanation:

Let p represent the population

in 1965 → the population becomes 2p

in 1970 → the population becomes 2(2p) = 4p

in 1975 → the population becomes 2(4p) = 8p

p  ——————> 100%

8p  ————-—-> x%

then

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