Question

the ratio of the sums of first n yerms of two AP is (5n-3):(7n+2). find the ratio of mth terms of these AP.

Answer 1

♠ REFER THE CLIPPING.

Answer 2

Let the mth terms be m1 for the first AP and m2 for the 2nd AP.

m1:m2=?

m1:m2

=a+(m1-1)d:a+(m2-1)d

Multiplying by 2:

=2a+2(m1-1)d:2a+2(m2-1)d

=n/2*[2a+(2m1-1-1)d]:n/2*[2a+(2m2-1-1)d]

This is the sum for the 2m1-1th term and 2m2-1th term

So :

S2m1-1th term:S2m2-1th term

=5(2m1-1)-3:7(2m2-1)+2

=10m1-5-3:14m2-7+2

=10m1-8 : 14m2-5

That m1 and m2 is same .

You can write it m I have just written to make sure that m1 is for AP1 and m2 is for AP2

That's the ratio: 10m-8:14m-5

Hope this helps