Can the linear model for a set of data that is presented in a scatter plot always be used to make a prediction about any x-value?

What is the quadric regression equation that fits these data

Write as a product: ac^2–ad+c^3–cd–bc^2+bd

Sally deposited money into a savings account paying 4% simple interest per year.the first year,she earned $75 in interest.how much interest will she earn during the following year?