The price of 8 citrons and 9 fragrant wood apples is 145 units. The price of 9 citrons and 8 fragrant wood apples is 144 units. Find the price of a citron and the price of a wood apple.

The price of a citron is 8 and the price of a wood apple is 9

Step-by-step explanation:

First of all we make two equations that represents the problem

c = citrons price

w = wood apples price

8c + 9w = 145

9c + 8w = 144

we clear c in the first equation

8c + 9f = 145

8c= 145 - 9w

c = (145 - 9w) /8

c = 145/8 - 9w/8

we replace c by (145/8 - 9w/8) in the second equation and solve

9(145/8 - 9w/8) + 8w = 144

163.125 - 10.125w + 8w = 144

163.125 - 144 = 10.125w - 8w

19.125 = 2.125w

19.125/2.125 = w

9 = f

now we replace w in the first equation

8c + 9w = 145

8c + 9(9) = 145

8c + 81 = 145

8c = 145 - 81

8c = 64

c = 64 / 8

c = 8

The price of a citron is 8 and the price of a wood apple is 9

part a

answer: a reasonable domain is where n is a real number. so n can be between 0 and 10. both endpoints are included.

work shown:

n is the number of days after the experiment starts. the smallest n can be is n = 0 which means that 0 days have gone by, and we're at the start. to find out how large n should be, then replace f(n) with 16.13 and solve for n. use logarithms to isolate the exponent.

f(n) = 12*(1.03)^n

16.13 = 12*(1.03)^n

16.13/12 = (1.03)^n

1.34416666666667 = (1.03)^n

(1.03)^n = 1.34416666666667

log[ (1.03)^n ] = log[ 1.34416666666667 ]

n*log[ 1.03 ] = log[ 1.34416666666667 ]

n = log[ 1.34416666666667 ]/log[ 1.03 ]

n = 10.0062999823929

this rounds to n = 10 which is fairly close but not 100% perfect. so this is the largest n can be.

note: if you plug n = 10 into f(n), you'll get roughly 16.127 which rounds to 16.13 (this comes up again in part c)

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part b

answer: the y intercept is 12. it represents the starting height of the plant in cm.

work shown:

plug n = 0 into the f(n) function. simplify

f(n) = 12*(1.03)^n

f(0) = 12*(1.03)^0

f(0) = 12*(1)

f(0) = 12

on day n = 0, aka the starting point, the height f(n) is 12 cm

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part c

answer: the average rate of change is approximately 0.43061036458991 (round however you need to). this represents the average growth rate from day n = 3 to day n = 10. so the plant grew roughly 0.43 cm per day during this timespan, assuming you round to 2 decimal places.

work shown:

compute f(3)

f(n) = 12*(1.03)^n

f(3) = 12*(1.03)^3

f(3) = 13.112724 < we'll use this later

compute f(10)

f(n) = 12*(1.03)^n

f(10) = 12*(1.03)^10

f(10) = 16.1269965521294 < we'll use this later

now use the formula below with a = 3 and b = 10

aroc = average rate of change

aroc = [ f(b) - f(a) ]/[ b - a ]

aroc = [ f(10) - f(3) ]/[ 10 - 3 ]

aroc = (16.1269965521294 - 13.112724)/(10 - 3)

aroc = 3.0142725521294/7

aroc = 0.43061036458991

round this however you need to

note: the plant grew approximately 3.01 cm over 7 days, so roughly 0.43 cm per day is the average growth rate (if you were to round to 2 decimal places).