What is the answer to this question

Find the roots of the polynomial function f(x) = x^3 + 2x^2 + x

Suppose that a households monthly water bill (in dollars) is a linear function of the amount of water the household uses (in hundreds of cubic feet, hcf). when graphed, the function gives a line with slope of 1.65. if the monthly cost for 13 hcf is $46.10 what is the monthly cost for 19 hcf?

Me. i can't figure out this question. give an explanation too. .