Question

What is the 19th term of the geometric sequence: -2, 4, -8, 16..

Answer 1

nth term of a geometric sequence is given by

\[a _{n} = a _{1} \times r ^{(n-1)}\] ; Where a 1 is the first term and r is the common ratio

Answer 2

whom if I am looking at this right -2, 4, -8, 16, -32, 64, -128, 256, -512, 1024, -2048, 4096, -8192, 16384, -32768, 65536, -131072, 262144, -524288. a quicker way to do this was if you were able to notice that your original problem looked like the exponent sequence of 2. Since most of us know that multiplying a negative w/ a positive will always come out negative on an odd number then u can just type in 2 the 19th power on your calculator. When the answer comes up just apply the negative sign to it and that's your answer.