What are the solutions to the equation?

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

Enter the number of complex zeros for the polynomial function f(x) = x 4+ 5x² +6

1c) the number 131 is a term in the sequence defined by the explicit rule f(n)=5n-4. which term in the sequence is 131? 2a) write the first four terms of the function f(n)=n^2-1 2b) what is the 10th term of the sequence defined by the explicit rule f(n)=n^2-1 2c) the number 224 is a term in the sequence defined by the explicit rule f(n)=n^2-1. which term in the sequence is 224?