Hello, juliak!
I don't agree with their answer.
You were doing fine, then ...
Geometric sequence: .
Find and hence find the term.
What i got was: . . . . . Good!
So: .
. . .
We have: .
sequence 40, -20, 10. -5... is geometric
find Un and hence find the 10th term
what i got was
u1 = 40
and r = 1/2
so --> un=u1xr^n-1
un=40x(-1/2)^10-1
un=-20^9
un= -0.00000000000512
but the correct answer is -5/256
--> could you tell me where i got wrong?
Notice the change of sign in the sequence, hence . But this is what you use then, so it must be a typo...
This is a mistake in manipulating powers : (I use to simplify the ratio).so --> un=u1xr^n-1
un=40x(-1/2)^10-1
un=-20^9
un= -0.00000000000512
but the correct answer is -5/256
--> could you tell me where i got wrong?