What substitution should be used to rewrite 4x^4-21x^2+20=0

The graph below represents the number of dolphins in a dolphin sanctuary. select all the key features of this function.

In a column proof the right column states your reasons

Hart manufacturing had six-month sales of $80 million, with $20 million of that amount from the internet. it set a goal to increase the percentage of total sales coming from the internet by 4 percent in the next six months. the results were total sales of $85 million. if the company meets its goal exactly, what will the dollar amount of internet sales be?