What’s the answer to the system of equation?

What is the standard form of -5x^2+2x^4-11+x^3+3x

Suppose you are an avid reader and are looking to save money on the cost of books instead of paying about $20 for each book, you decide to look into purchasing a kindle for $120 you can purchase e-books for about $5 each 1. find the slope-intercept equation for the cost of the hard copy of books using x to represent the number of books 2. find the slope-intercept equation for the cost of the kindle with cost of e-books using x to represent the number of books

Rewrite the following quadratic functions in intercept or factored form. show your work. f(x) = 3x^2 - 12