how do you find explicit formula answer

Question

11,1,-9,-19,-29

 

Answer 1

An=a+d(n-1)

An=11+(-10)(n-1)

An=11-10n+10

An=21-10n

check:

n=1, An=21-10(1)=21-10=11

n=2, An=21-10(2)=21-20=1

n=3, An=21-10(3)=21-30=-9

n=4, An=21-10(4)=21-40=-19

n=5, An=21-10(5)=21-50=-29

Answer 2

You have to employ the formula

 

Explicit formula is given as a_n = a₁ + (n – 1)d

 

From the given sequence: 11,1,-9,-19,-29

 

a = 11, d = 10 and n = 5

 

 

 

a_n = 11 + (n – 1)10

 

 

a_n = 11  +10n - 10

 

a_n = 10n - 1     and that is your explicit formula.