I really need help on this question.!

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

Julie goes to the sports store and spends $40.50 before tax. she buys a pair of shorts for $21.75 and 3 pairs of socks that each cost the same amount. how much does each pair of socks cost? $$

Why is x= 4 a solution to the proportion 14/x 56/1 6