Question

If an ap the sum of first ten terms is 4 times the sum of first five terms then the ratio of first term and common difference is

Answer 1

10/2(2a+(10-1)d)=4(5/2(2a+(5-1)d))

5(2a+9d)=10(2a+4d)

2a+9d=2(2a+9d)

2a+9d=4a+18d

-2a=9d

a/d=-9/2