Question

Find S7 if t3=20 &t6=160

Answer 1

Answer:

S₇=635

Step-by-step explanation:

t₃=ar²=20

t₆=ar⁵=160

by dividing both eqaution, we get

r=2

a=5

• r>1, so S₇=a*(rⁿ-1/r-1)

• S₇=5*(2⁷-1/2-1)

• S₇=5*(128-1/1)

• S₇=5*127

• S₇=635(ans)