Having trouble with the following -doesn't seem to be enough information:
A geometric progression has first term a and common ration r. The sum of the first three terms is 4.88 and sum to infinity is 10.
1) Write down two equations involving a and r 9 I can do that bit: a=ar=ar^2 = 4.88 and a/(1-r) = 10
but then it asks: Show that 1-r^3 = 0.488 -can't seem to get that!
2) Then it asks: mk(Subscript) is the kth term calculate the sum to infinity of mk^2.
Thanks for any help here!
A geometric progression has first term a and common ration r. The sum of the first three terms is 4.88 and sum to infinity is 10.
1) Write down two equations involving a and r 9 I can do that bit: a=ar=ar^2 = 4.88 and a/(1-r) = 10
but then it asks: Show that 1-r^3 = 0.488 -can't seem to get that!
2) Then it asks: mk(Subscript) is the kth term calculate the sum to infinity of mk^2.
Thanks for any help here!