#1**+1 **

11) The common ratio should be - 5. So, you would have the sequence of:

37, - 185, 925, - 4,625........etc.

12)

N=(L - F) / D + 1, where N=Number of terms, L=Last term, F=First term, D = Common difference

N=(65 - (-5)) / 5 +1

N = 15 - Number of terms

Sum = (F + L) / 2 x N

Sum = (-5 + 65) / 2 x 15

Sum = (60) / 2 x 15

**Sum = 450**

Guest Mar 19, 2018

#2**+1 **

GP 37, ... 925

925/37=25

So the common ratio must be a factor of the form 25 to the power of some number

The obvious ones to try are \(\pm25\;\;or\;\; \pm5\)

-185/37 = -5 could be that one

-4625/37 = -125 = (-5)^3 or that one

-925/37 = -25 = (-5)^2 or that one, no that cannot work, just by inspection.

481/37 = 13 not that one

37, 37*-5, 37*-5*-5,.....

37, ** -185**, 925, ** -4625**,

so there are two answers and both have the common ratio of -5

Melody
Mar 19, 2018