Question

Find the 26th in the arithmetic sequence: -15,
-35, -55, -75,...
​

Answer 1

Answer:

We know that,

d=a2-a1

let,

a1=-15,a2=-35

d=--35-(-15)

d=-35+15

d=-20

a26=a+25d

a26=-15+25(-20)

a26=-15-500

a26=-515

Answer 2

Answer:

a=-15

d= t2-t1 = -35-(-15)=-35 + 15 = -20

tn=a +(n-1)d

t26= -15 + (26 - 1) -20

=-15 + 25 × -20

=-15 + (-500)

=-15 - 500

= -515

(therefore symbol) t26 = -515

(therefore symbol) The 26th term in the A.P. is -515