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

What values of x satisfy the inequality x^2-9x< 0? how is your answer shown on the graph?

Do some research and find a city that has experienced population growth. determine its population on january 1st of a certain year. write an exponential function to represent the city’s population, y, based on the number of years that pass, x after a period of exponential growth. describe the variables and numbers that you used in your equation.

If rt is greater than ba, which statement must be true ?