Question

Given an=84, d=2,sn=-14​

Answer 1

Answer:

000oooooo

Step-by-step explanation:

this answer is 000

Answer 2

Answer:

sorry, I don't like to solve thhe quadratic equation.

i hope you can solve it.....

Step-by-step explanation:

we have

an=84

a+(n-1)d=84

a+(n-1)2=84. we have d=2

a+2n-2=84

a+2n=86

a=86-2n. (1)

we also have

sn=-14

n/2(2a+(n-1)d)=-14

n/2(2a+(n-1)2=-14

n(2a+2n-2)=-28

n(2(86-2n)+2n-2)=-28. (using 1)

n(172-4n+2n-2)=-28

n(170-2n)=-28

170n-2n²=-28

-(2n²-170n)=-28

2n²-170n=28

2n²-170n-28=0

you can solve this equation then you can get the answer