Pls help me fast, math lesson 1.07 k12

Use mathematical induction to prove the statement is true for all positive integers n, or show why it is false. 1^2 + 4^2 + 7^2 + + (3n - 2)^2 = [n(6n^2-3n-1)/2]

The salesperson earns a 5% commission on the first $5,000 she has in sales. the salesperson earns a 7.5% commission on the amount of her sales that are greater than $5,000. this month the sales person had $8,000 in sales. what amount of commission, in dollars, did she earn?

Which statement is true about the function f(x)= square root -x ? the domain of the graph is all real numbers. the range of the graph is all real numbers. the domain of the graph is all real numbers less than or equal to 0. the range of the graph is all real numbers less than or equal to 0.