Find the arithmetic series, find s25 ! show work

21)

 = a₁ + d(n - 1)  ; where a₁ is the first term and d is the difference.

a₁ = 3, d = 4    →    = 3 + 4(n - 1)   = 3 + 4n - 4   = 4n - 1

= 4(25) - 1   = 100 - 1   = 99

 =

 =  = = 51 · 25  = 1275

= 4n - 1  ,  1275

23)

 = a₁ + d(n - 1)  ; where a₁ is the first term and d is the difference.

a₁ = 4, d = 10    →    = 4 + 10(n - 1)   = 4 + 10n - 10   = 10n - 6

= 10(25) - 6   = 250 - 6   = 244

 =

 =  = = 124 · 25  = 3100

= 10n - 6  ,  3100

answer: 7 x 2/5 = 2.8 hours, is your answer. your welcome! : 3

step-by-step explanation: first work out how long it took to hose 1/7 of the lawn which is 2/5 hours. times that by 7 to get the whole lawn.

sorry i don't know the other answer. i didn't learn what a proportional relationship is.