# How do you find the missing term in the geometric sequence: #-5, 10, -20, 40, __#?

##### 1 Answer

Oct 31, 2016

#### Explanation:

The standard

#color(blue)"geometric sequence"# is.

#a,ar,ar^2,ar^3,............ , ar^n# where r is the common ratio.

and

#r=a_2/a_1=a_3/a_2=........ =a_n/(ar_(n-1))# here

#r=10/(-5)=(-20)/10=-2# Hence to find the missing term, multiply the previous term by r.

#rArra_5=-2xx40=-80#